Only 1% could solve this insanely difficult problem

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  • Опубликовано: 16 сен 2024
  • If this question is easy for you, I see great things for your future. Thanks to Rahul and Battu for the suggestion! This problem appeared on the 2022 JEE Advanced Paper 1 Mathematics section as Question 8. The JEE Advanced is an extremely difficult exam for admission into India’s prestigious IIT schools. I think this is one of the easier questions of the paper. I give credit to the Unacademy Atoms video about the paper which helped me understand how to solve the problem.
    2022 JEE Advanced paper 1 answer sheet (see Q.8)
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Комментарии • 390

  • @pas1033
    @pas1033 Год назад +139

    Damn, who would have guessed 4 years ago that a question from the exam which decided my college would appear in this channel? I scored barely 35% in this Maths paper, and 50% overall, and am now in a good IIT!

    • @louvskth7141
      @louvskth7141 Год назад +19

      im currently training for jee and im somewhat relieved to hear this 😭

    • @kuch.bhi8847
      @kuch.bhi8847 Год назад +11

      In jee advanced, good percentage is almost impossible, rather a good percentile matters

    • @anmolroy2831
      @anmolroy2831 Год назад +7

      Which college and which branch?

    • @anonymous_4276
      @anonymous_4276 Год назад +2

      This makes me feel embarrassed. Back when I had attempted it, I had gotten about 70% in maths but borderline failed chemistry.

    • @pas1033
      @pas1033 Год назад +1

      @Anmol Roy I won't name the IIT for privacy reasons. But I'm in the EE branch.

  • @anil2296
    @anil2296 Год назад +272

    According to JEE Advanced 2022 report, only 0.95% of the candidates have answered this question correctly.

  • @MarieAnne.
    @MarieAnne. Год назад +63

    Using coordinate geometry:
    A = (0,0), B = (1,0), C = (0,3), M (midpoint of BC) = (1/2, 3/2), BC = √(AB²+AC²) = √(1²+3²) = √10
    Larger circle has center (1/2, 3/2) and radius R = BC/2 = √10/2
    Smaller circle has center (r, r) and radius r (since it is tangent to both the x-axis and y-axis).
    For circles that are internally tangent, distance between centers = R - r
    √((1/2 - r)² + (3/2 - r)²) = √10/2 - r
    (1/2 - r)² + (3/2 - r)² = (√10/2 - r)²
    1/4 - r + r² + 9/4 - 3r + r² = 10/4 - r√10 + r²
    r² = 4r - r√10
    Since r ≠ 0, divide both sides by r
    r = 4 - √10
    The calculations are pretty much the same as in the video, but I find the setup a little simpler.

    • @dadasdadas2044
      @dadasdadas2044 Год назад +4

      Hello
      Can you help me ?
      I want solve this but I cann't
      x+y+z=15
      Xsquare +Ysquare+Zsquare=75
      X=?
      Y=?
      Z=?

    • @Mission-SSC-CGL2024
      @Mission-SSC-CGL2024 Год назад +1

      @@dadasdadas2044 x=y=z=5

    • @muhammadaryasaputra6754
      @muhammadaryasaputra6754 Год назад +4

      @@dadasdadas2044 You can't and we can't because there aren't enough information

    • @MeowUnderBlanket
      @MeowUnderBlanket Год назад +4

      @@dadasdadas2044 bro it's a hit and trial question.
      If you put 5 in place of x, y and z, it satisfies both equations.
      There's the answer

    • @AlchemistOfNirnroot
      @AlchemistOfNirnroot Год назад

      @@MeowUnderBlanket I don't seem to be able to find an algebraic way of doing it. It's just a plane intersecting a sphere at a single point.

  • @sweepingtime
    @sweepingtime Год назад +184

    Setting up the diagram is the key to getting the solvable equations. It was tedious enough to be difficult, and oh boy this was the easiest question on that paper...

    • @Hdhshsbssjsjsj
      @Hdhshsbssjsjsj Год назад +5

      Very true.

    • @biswakalyanrath966
      @biswakalyanrath966 Год назад +5

      Easiest was the question from permutations are combinations

    • @TechyMage
      @TechyMage Год назад +5

      Easiest was from logarithm and probability and trigonometry and venn diagram

  • @itsOnlyPIYUSH
    @itsOnlyPIYUSH Год назад +167

    I also gave this year 2022 Jee Advanced and I am happy to tell you @MindYourDecisions that this questions has taken my 3 mins of Precious time and the result was Amazing . LoL 😁

    • @sriprakash7245
      @sriprakash7245 Год назад +5

      Did u landed into any IIT then?

    • @itsOnlyPIYUSH
      @itsOnlyPIYUSH Год назад +16

      @@sriprakash7245 Hell Yes I'm studying right now thats why I'm able to answer so late. 😊

    • @sriprakash7245
      @sriprakash7245 Год назад +6

      @@itsOnlyPIYUSH congratulations

    • @kumarsumit9448
      @kumarsumit9448 Год назад +6

      Bhaiya aap kis iit me ho

    • @itsOnlyPIYUSH
      @itsOnlyPIYUSH Год назад

      @@sriprakash7245 Thanks.

  • @cblpu5575
    @cblpu5575 Год назад +42

    I solved this using coordinate geometry. It is less elegant however very little brainpower is needed which can be helpful in nervous exam situations.
    Let vertices of the right angled triangle be (3,0),(0,0),(1,0).
    The circumcenter simply by its definition is (1/2,3/2). The circumcircle also passes through (0,0). So we get that the equation of the circle is x^2+y^2-x-3y=0
    Now let the circle whose radius we want be x^2+y^2+2gx+2fy+c=0
    Now it touches the coordinate axes at two points say (x_1,0),(0,y_1). Putting these points we get two quadratic equations in x_1 and y_1 whose discriminant is 0. Therefore we get that g^2=c=f^2 => g=f
    Now the circles touch internally. This means the distance between their centres c_1 and c_2 is equal to the difference of the radius of the larger circle and the smaller circle.i.e, C_1C_2= r_1-r where r_1 is the radius of the circumcircle. [(1/2-g)^2+(3/2-f)^2]^(1/2) = √10/2 - √(-c+g^2+f^2).
    But, g^2-c=0 and g^2 = f^2
    This allows us to completely simplify the expression into the quadratic equation
    f^2+f(√10-4)=0
    From here we obtain that f = 4-√10. since the radius of the circle is √(-c+f^2+g^2) and -c+g^2 =0, we have the radius = 4-√10

  • @bdot02
    @bdot02 Год назад +277

    I can confidently say there was no way I could have solved this.

    • @patrickng8974
      @patrickng8974 Год назад +7

      but I have solved this quite quickly.😅

    • @bdot02
      @bdot02 Год назад +13

      @@patrickng8974 honestly I've never seen the "arc BAC = π/2" before and with hindsight I can see that it means that it's a 90° angle, I still wouldn't have been able to get further than that point in the puzzle. But that's what most of us are here for, to learn and figure these things out.

    • @Aditisoukar
      @Aditisoukar Год назад +1

      Yes me too i just ignored this question like every other question in the math section 😅

    • @arolimarcellinus8541
      @arolimarcellinus8541 Год назад +3

      @@patrickng8974 like how?? Many normal high school student cannot even understant that tangent line between two circle, even more conceptualize the triangle inside the circle. Like, it straight up competition level knowledge

    • @lgooch
      @lgooch Год назад

      @@arolimarcellinus8541 I’m in middle school and solved it, and yes, I do competition math

  • @Aditisoukar
    @Aditisoukar Год назад +251

    I gave jee advanced this year and skipped all maths questions except 4 which i attempted just to qualify 😂

    • @omdave1008
      @omdave1008 Год назад +15

      Can't be more same 😂

    • @blue_g29
      @blue_g29 Год назад +6

      What rank did you get in jee mains?

    • @Aditisoukar
      @Aditisoukar Год назад +3

      @@blue_g29 53440 was my rank in jee mains

    • @blue_g29
      @blue_g29 Год назад +5

      @@Aditisoukar i am 2023 aspirant and i am fearing of jee mains too much ..can you help me with this?

    • @leif1075
      @leif1075 Год назад

      How can you just skip it? Is thst even allowed?

  • @mihaiio82
    @mihaiio82 Год назад +36

    I am impressed that you used the module, |r - 1.5|. Very nice.

    • @fili3907
      @fili3907 Год назад +1

      Well that's a good habit to take to use modules when you want a difference and don't know which term is the greater (when, let's say, one of them is a variable or is unknown).
      But it was quite useless here, we know r < 1.5 (because r is the length of the square and is smaller than both sides of the triangle) and we'll square it anyways.

  • @ayushrajput6354
    @ayushrajput6354 Год назад +17

    We can use coordinate geometry in this question two sides of triangle as y and x axis and the center of smaller circle will lie on y=x
    Result will be 4- √10

    • @soundsinteresting208
      @soundsinteresting208 Год назад

      How it will lie on y=x

    • @ayushrajput6354
      @ayushrajput6354 Год назад

      @@soundsinteresting208
      Two sides of triangle are perpendicular and the circle (not circumcircle) touch the sides (y and x axis ) in this case center of circle will on y=x axis

  • @rcht958
    @rcht958 Год назад +20

    Ah yes, me watching JEE videos after JEE

  • @lapaget1
    @lapaget1 Год назад +22

    There is also a formula for this problem. It's r = a + b - c. Applying with a=1, b=3, c=√10, then r= 1+3-√10 = 4-√10

    • @Cooososoo
      @Cooososoo Год назад +10

      From where this formula has come could you tell please

    • @sayonmondal3454
      @sayonmondal3454 Год назад

      @@Cooososoo just take the side lengths as variables and solve it like in the video

    • @sayonmondal3454
      @sayonmondal3454 Год назад +2

      @@Cooososoo MD = c/2 - r, ME = |a/2-r| and DE = |b/2 - r|, Pythagoras theorem
      c²/4 + r² - rc = a²/4 + r² - ra + b²/4 + r² - rb
      As a²+b² = c² they cancel out
      r(r-a-b+c) = 0
      r = a+b-c

    • @musaratjahan7954
      @musaratjahan7954 Год назад +4

      The formula is 2r=a+b-c and its for an incircle. This isn't an incircle

  • @anuragsingha4557
    @anuragsingha4557 Год назад +71

    I scored only 15 marks in math.Physics and chemistry saved my rank

  • @gen3360
    @gen3360 Год назад +9

    I haven't normally encountered such type of qs in pyqs, this does however remind me a lot of ioqm pattern papers. Certainly using those techniques helped in solving the question.

  • @moisesbarrera4849
    @moisesbarrera4849 Год назад +18

    Beautiful solution sir. Thank you. Greetings from México City.

    • @carultch
      @carultch Год назад

      Salutaciones Señor.

  • @t3mpt397
    @t3mpt397 Год назад +11

    i remember solving this question in JEE ADVANDED this year
    took a little time... but eventually did it

    • @vampire9355
      @vampire9355 Год назад

      Hey dude, how can angle BAC be π/2

    • @angelinageorge2278
      @angelinageorge2278 Год назад

      @@vampire9355 look in radians we say pi/2 is 90 degree

  • @Tribal260
    @Tribal260 Год назад +12

    That was pretty simple. I just had to watch the video and got the answer!

  • @jasnoorsingh4442
    @jasnoorsingh4442 Год назад +33

    Tbh using coordinate geometry is made it pretty easy than thinking about all this stuff

  • @mr_angry_kiddo2560
    @mr_angry_kiddo2560 Год назад +53

    Hi Sir iam Battu , thank for providing the solution ☺️

  • @Random-jd1yr
    @Random-jd1yr Год назад +4

    More generally, one can show the following: Let ABC be a triangle with side lengths a=BC, b=CA, c=AB, and let r denote the radius of the circle tangent to AB, AC, and internally the circumcircle.
    Then r=sqrt((s-b)(s-c)/(s(s-a)))bc/s (with semi-perimeter s). Moreover, if BAC is a right angle, then r=2(s-a)=b+c-a.
    To see this, denote by M the midpoint of this circle k, E the the center of the excircle of ABC opposite A, g the angle bisector of angle BAC, X the intersection of k and line segment AM, Y the intersection of this excircle and line segment AE, Z the intersection of this excircle and g not lieing on the line segment AE.
    Invert at a circle centered at A with radius 1. This sends B to B' on ray AB with AB'=1/c, and C to C' on ray AC with AC'=1/b. This maps the circumcircle of ABC to the line B'C', and the lines AB and AC are mapped to AB', AC' (i.e. to themselves). Consequently, k is mapped to some circle k' tangent to lines AB', AC', B'C' and situated outside(!) triangle AB'C' (since k is tangent internally(!) to the circumcircle of ABC). That is to say, k' is the excircle of triangle AB'C' opposite A.
    Now follow up with a reflection across the line g and a homothety centered at A with factor bc. Since AB'=1/c, AC'=1/b, this second map sends B' to C, C' to B and consequently triangle AB'C' to ACB and thus k' to the excircle of ABC opposite A.
    Since both of these maps leave the line g invariant, one can see that their composition takes X to Z. Thus, bc/AX=AZ (1).
    Let Q denote the tangent point of the excircle opposite A with line AB. By secant theorem, AY*AZ=AQ^2 (2). It is well-known that AQ=s, where s is the semi-perimeter.
    Let I denote the center of the incircle of ABC, W the intersection of the incircle and line segment AI, and P the tangent point of the incircle on line AB. Let R denote the radius of the incircle.
    Since both k and the incircle are tangent to AB and AC, one has r/R=AX/AW (3).
    Since both the in- and excircle are tangent to AB and AC, one has AW/AY=AP/AQ=(s-a)/s (4) (using the well-known AP=s-a, AQ=s).
    Combining (1), (2), (3), and (4) one obtains
    r=R AX/AW=R (AX/AY) (AY/AW)=Rbc/(AY*AZ) s/(s-a)=Rbc/(s(s-a)).
    Let F denote the area of ABC. Then F=sR.
    Therefore, r=(F/s)bc/(s(s-a)).
    If ABC is right-angled in A, then F=bc/2. Moreover, 4s(s-a)=(-a+b+c)(a+b+c)=-a^2+(b+c)^2=-a^2+b^2+c^2+2bc=2bc (by Pythagoras's theorem), so s(s-a)=F. Thus, r=(F/s)bc/F=bc/s=2F/s=2(s-a)=b+c-a.
    If ABC is not assumed to be right-angled in A, one may instead apply Heron's formula for F to conclude
    r=sqrt{(s-b)(s-c)/(s(s-a))}bc/s

  • @SirNobleIZH
    @SirNobleIZH Год назад +6

    I got close, through clever reasoning, I determined that r must be between 0.5 and 1 exclusively, but couldn't narrow it past that

  • @ThanksThanks-en9no
    @ThanksThanks-en9no Год назад +8

    You could have did it like assuming a as origin and writing coordinates of both centres then c1c2=r1-r3

    • @apexxvinit2201
      @apexxvinit2201 Год назад

      Yes but classic geometry is far better than coordinate

  • @HARSHSINGH-kg6gc
    @HARSHSINGH-kg6gc Год назад +8

    I got this correct in jee advanced 2022 😀

  • @shrujankharwadey8769
    @shrujankharwadey8769 Год назад +56

    I faced this question 🙋this year

  • @piyushkumarjha599
    @piyushkumarjha599 Год назад +18

    Remeber the stuff , this has a another approach by mixtilinear incircles , a general problem was in rajeev manocha and similar came in AIME

    • @MindYourDecisions
      @MindYourDecisions  Год назад +8

      I had never heard the term mixtilinear circles before, interesting. mathworld.wolfram.com/MixtilinearIncircles.html

    • @piyushkumarjha599
      @piyushkumarjha599 Год назад +2

      @@MindYourDecisions woah! Loved your approach , one of my friend suggested the length chase and i loved it , for first attempt i did by mixitilinear incircles!

    • @techmaster6587
      @techmaster6587 Год назад +2

      @@piyushkumarjha599 dude, Are you Jee Aspirant ...???

    • @piyushkumarjha599
      @piyushkumarjha599 Год назад

      @@techmaster6587 no

    • @piyushkumarjha599
      @piyushkumarjha599 Год назад

      @@HimanshuRajOk yes?

  • @wheresmywatergameplay2004
    @wheresmywatergameplay2004 Год назад +11

    I have a question suggestion: how to divide a circle in three parts of equal areas using only 2 lines

    • @animarcs
      @animarcs Год назад +2

      The two lines will be secants passing through a common point on the circumference

    • @DendrocnideMoroides
      @DendrocnideMoroides Год назад

      my solution (assuming the circle is centered at the origin and has radius r) make 2 vertical lines one at x=-0.264932084602777*r and the other at x=0.264932084602777*r
      that number is the solution of this equation (arcsin(x) + x*sqrt(1-x²) = pi/6)

  • @vedants.vispute77
    @vedants.vispute77 Год назад +6

    I took a different approach here. Actually I got it wrong, but its really was hard to find out the mistake if you do it by your own rough diagram. Try it by not looking at myd's diagram or you gotcha. Extend the sides AC and AB and joined the points B' and C' such that the tangent at the point where the both circles meet coincide B'C' ; then smaller circle works like a incircle and we can work out its extended sides and compute radius of circle by conserving area.

    • @carultch
      @carultch Год назад

      How long would the altitude to the hypotenuse be, on the triangle in your profile picture?

    • @notananimenerd1333
      @notananimenerd1333 Год назад

      Hey vedant did you answer ioqm this year? If yes what was your score?

    • @vedants.vispute77
      @vedants.vispute77 Год назад

      @@notananimenerd1333 ah dude I remember you! I didn't gave ioqm, coz i would need to prepare for it separately than jee which is not for me.. and it requires big brains..

    • @vedants.vispute77
      @vedants.vispute77 Год назад

      @@carultch i/0, which is.. *_*

    • @notananimenerd1333
      @notananimenerd1333 Год назад

      @@vedants.vispute77 oh I see.. you ought to check the paper man.. it is considered as one of the toughest ioqms (prmos ) of all times 😬

  • @divyanshsrivastava824
    @divyanshsrivastava824 Год назад +3

    can also do by coordinate easily as we know circumcentre coordinates and internally tangent circle condition is c1c2= r1-r2

  • @johnchessant3012
    @johnchessant3012 Год назад +2

    it's just r = x + y - sqrt(x^2+y^2)

  • @aviralmishraofficial1626
    @aviralmishraofficial1626 Год назад +8

    I gave this exam this year
    Got 102 marks which fetches around 7500 rank out of 2,25,000 candidates who wrote it

  • @MehdiMalekip
    @MehdiMalekip Год назад +1

    The general solution is interesting r=a+b-c, where c is the hypotenuse!

  • @DamnBoii123
    @DamnBoii123 Год назад +14

    Damn I couldn't solve it during the exam 🙂

  • @rogiervankoetsveld741
    @rogiervankoetsveld741 Год назад +3

    The vertical distance of MD is not r-1.5 but 1.5-r. Since it gets squared later, this results in the same thing but still

  • @randomjudgements8852
    @randomjudgements8852 Год назад +1

    WE KNOW IT BETTER FROM THE PERSPECTIVE OF COORDINATE GEOMETRY... WE ASSUME A TO BE ORIGIN AND AB AND AC BE THE COORDINATE AXIS THEN THE QUESTION TAKES ONLY 30 SECONDS...

  • @jamessanchez3032
    @jamessanchez3032 Год назад +4

    If r=0 WAS allowed, would that mean that the second "circle" was point A?

  • @surendrakumardubey1605
    @surendrakumardubey1605 Год назад +3

    I love your humbleness

  • @handanyldzhan9232
    @handanyldzhan9232 11 месяцев назад

    Some simple applied integral: divide the area into immeasurably thin rings parallel to the perimeter. Go progressively inside from there, ending up at the center of the inner circle. Then the formula of the relationship between the perimeter, area and inner circle will become clear.

  • @rajatgupta7296
    @rajatgupta7296 Год назад +1

    Didn't solv this in the exam hall but now I m happy to be in iit Guwahati

  • @elimin8tor
    @elimin8tor Год назад +4

    i was able to pretty much follow everything until r = 4 - Sq10. It seemed like a big unexplained jump :(

    • @ThePaliwalie
      @ThePaliwalie Год назад +2

      Starting from r(r-4+sq10) = 0. As r > 0, both sides can be divided by r, resulting in: r-4+sq10 = 0 or r = 4-sq10

    • @elimin8tor
      @elimin8tor Год назад +1

      @@ThePaliwalie Oh my days. If I'd spent 10 seconds thinking about it I would have got that... it was early in the morning for me - that's my excuse. Thanks!

  • @dakshkothari6657
    @dakshkothari6657 Год назад +12

    Just remember! You have to think and solve the question AND you should know the value of rt.10 correctly upto 2nd decimal, all within 3 minutes.

    • @juvituhey752
      @juvituhey752 Год назад +2

      didnt need to know root 10. Writting 4 - root(10) was enough.

    • @silphate9836
      @silphate9836 Год назад +8

      you don't have to do it within 3 mins, not only do u not have to solve all the questions in the exam, it's almost never a good idea to do so, even doing half the questions is considered to be really good+ some questions obviously take more time than others and maths generally has the most lengthy quesions so....3 mins is very over exagerrated

    • @soumalyanandi6175
      @soumalyanandi6175 Год назад

      No need to solve all problems

  • @harshitmahajan9196
    @harshitmahajan9196 Год назад +1

    But they give this is 2place decimal which which made many people do incorrect

  • @anonymous_4276
    @anonymous_4276 Год назад

    At the end instead of focusing on the small right triangle, you can also use the intersecting chords theorem to get the answer. That's what I did.

  • @Mrpuffin001
    @Mrpuffin001 Год назад +5

    Damn.... nostalgia's hitting me hard now ......i literally attempted this question in jee adv22.....don't remember if I got the correct answer though😂

  • @randerson4009
    @randerson4009 Год назад +1

    . . . which happens to be twice the radius of the inscribed circle!

  • @TomKaren94
    @TomKaren94 Год назад +2

    The problem doesn't say the angle was measured in radians.

    • @eroraf8637
      @eroraf8637 Год назад +8

      It’s expressed in terms of pi with no unit. It doesn’t get much more explicit than that. You don’t say that a right angle is ninety, with no units, do you?

  • @pkhisanjeevkumar2048
    @pkhisanjeevkumar2048 Год назад +1

    Following you since 2020

  • @techmaster6587
    @techmaster6587 Год назад +12

    Brother, can you solve the complete paper of JEE Advanced in just 1 hour??? Please

  • @howareyou4400
    @howareyou4400 Год назад

    Pretty sure this is a grade 9 difficulty problem. It's not easy for an normal grade 9 students but considered medium difficulty for any good high school students.
    After all you just set the center of the circle's coordinates as (x, y) and pretty mechanically writing down the 3 equations to get r = BotSide + LeftSide - Hypo

  • @agastyavalisetty8620
    @agastyavalisetty8620 Год назад +1

    man u can use the circumcenter coordinate geometry principle where the center of the circucircle lies on intersection of perpendicular bisectors of sides or even better jus use the distance formula take a point (h,k) and equate its distances from each vertex(cuz radius of circle is equal) its a wayyy more practical way to solve this qs

  • @shockshwat236
    @shockshwat236 Год назад +3

    in 5:00 shouldnt ME be 1.5 - r since 1.5 is the bigger value than r?
    I get it that after squaring it it won't matter but still it's wrong

    • @harshagarwal3045
      @harshagarwal3045 Год назад

      In the video, it is in modulus so it doesn't matter

  • @acarbonbasedlifeform70
    @acarbonbasedlifeform70 2 месяца назад

    So that's why they specified the radius should be greater than 0...

  • @yanco6
    @yanco6 Год назад +1

    ME = 1.5 - r
    But this is not changing the outcome because the power of 2

  • @starpawsy
    @starpawsy Год назад +2

    It's unfair asking a question in this way. Really needs a diagram.

    • @carultch
      @carultch Год назад

      I think the challenge is to come up with the diagram. The only part of the question I could see that really needs clarification, is that the word "touches" is vague. Really should say that the two circles are tangent to each other, since tangent has a more precise meaning than "touches". I'm aware that the namesake of the word tangent, is "to touch", so you could infer that they meant to specify it that way.

  • @EliasSipsTea7030
    @EliasSipsTea7030 Год назад +2

    I would like it if you reformulated the question because "touches" isn't that accurate of a word , good video tho.

    • @rakshithbs1642
      @rakshithbs1642 Год назад

      What was your initial thought when it said "touches"? I'm just curious to see how else it translates in this context....

    • @EliasSipsTea7030
      @EliasSipsTea7030 Год назад +1

      @@rakshithbs1642 touches meant to me : they share at least one point, so them being tangente isn't the only option but the first option

    • @rakshithbs1642
      @rakshithbs1642 Год назад

      @@EliasSipsTea7030 Fair enough, but the definition of tangent is that it "touches" a curve at a point.
      Wiki definition: "In geometry, the tangent line (or simply tangent) to a plane curve at a given point is the straight line that "just touches" the curve at that point."

  • @HemantPandey123
    @HemantPandey123 Год назад +4

    You can also use coordinate geometry. Centers are (0.5,1.5) and (r,r). Now use CC1 = MT-DT result. Same result. We don't even need to draw topologically correct diagram. Just saves time.

    • @leif1075
      @leif1075 Год назад

      What does CC1 MT DT mean?

    • @kongkonasahadola2949
      @kongkonasahadola2949 Год назад

      How is center of the 2nd circle (R,R) and not ( R1, R2)?

    • @kongkonasahadola2949
      @kongkonasahadola2949 Год назад

      @@leif1075 the distance between two circle's center, CC1 = subtraction of the two radius ( MT - DT ) ....as the circles touched internally

    • @HemantPandey123
      @HemantPandey123 Год назад

      @@kongkonasahadola2949 It touches both the axes. Hence radius are same.

    • @leif1075
      @leif1075 Год назад

      @@kongkonasahadola2949 oh you never said what DT and MT were that's why so.dont think anyone would understand...ty for clarifying

  • @ved9402
    @ved9402 Год назад +2

    The hardest part was to find value of 4-√10 without calculator in examination hall and correctly upto 2 digits
    Why don't you try other questions 🤪

  • @thunderskull258
    @thunderskull258 Год назад +9

    NV SIR ON TOP ⚛️ ⚛️ ATOMS OP 🔥🔥

  • @cantosoares
    @cantosoares Год назад +4

    Pela construção geométrica é irrelevante escrever em módulo a diferença entre os lados já que é visível qual lado é maior que o outro. Inclusive foi utilizado a visualização em relação aos raios da circunferência.
    Abraço

  • @trilokvyas7987
    @trilokvyas7987 Год назад

    loved it man

  • @RaiAdarsh-bi8bh
    @RaiAdarsh-bi8bh Год назад

    problem was only knowing the value of root 10 as it was not provided in the question

  • @abhay6576
    @abhay6576 Год назад +39

    It would've been much easier with coordinate geometry

  • @WisdomFromAshes
    @WisdomFromAshes Год назад +3

    Excellent. Now can you tackle Twitter?

  • @proffessorclueless
    @proffessorclueless Год назад +2

    It would have been instructive to see the circle of r not >0 in the solution.

    • @smsn13act85
      @smsn13act85 Год назад +1

      r=0 is a solution. It touches all the required things at A so needed to be excluded.

  • @YashGupta-zn6wf
    @YashGupta-zn6wf Год назад

    I gave JEE Advanced 2022, did not solve this question, still got selected and now sitting in IIT Kharagpur.

  • @Indian_Ravioli
    @Indian_Ravioli Год назад

    Great solution.

  • @Swaroop704
    @Swaroop704 7 месяцев назад

    This question is just so easy, i solved it using basic coordinate geometry

  • @huzefa6421
    @huzefa6421 Год назад

    Good to see indian unacadamy being featured

  • @soumalyanandi6175
    @soumalyanandi6175 Год назад +2

    It was easier with coordinate geometry

  • @enamorezpascal5191
    @enamorezpascal5191 Год назад +1

    The problem is hard to understand.

  • @shuhuasong1829
    @shuhuasong1829 Год назад

    2r=a+b-c, c=\sqrt{a^2+b^2}

    • @advaykumar9726
      @advaykumar9726 Год назад

      That is incircle radius formula
      Incircle touches all the sides but in the question the circle touches only two sides
      Hence we can't apply this formula

  • @cowofthemonth
    @cowofthemonth 7 месяцев назад

    It's exactly twice the inscribed circle radius. I wonder if that's true for all right triangles?

  • @wesleydeng71
    @wesleydeng71 Год назад

    More generally, r = AB + AC - BC.

  • @dilipkumarpatel481
    @dilipkumarpatel481 Год назад +3

    If this question is easy,
    What is the definition of hard?

    • @prathamkalgutkar7538
      @prathamkalgutkar7538 Год назад +2

      Something like this and more :
      If f(x) is a differentiable function and g(x) is a double differentiable function such that |f(x)|≤1 and f'(x)=g(x) . If f2(0)+g2(0)=9 . Prove that there exists some c∈(-3,3) such that g(c).g''(c)

  • @rohangeorge712
    @rohangeorge712 Год назад

    solved it the same way, although it took me like 7 minutes whereas in the competition i think u would have like 3 minutes or something to do this problem

  • @celia222
    @celia222 Год назад

    I’ve been in construction so long I’ve forgotten to default to radians. 😅

  • @codewizstw
    @codewizstw Год назад +1

    I didn't know that "touches" was the same as "tangent". sigh

    • @carultch
      @carultch Год назад

      Touching is the namesake of the word tangent. It is a little unclear to specify the tangency of the circles with the word "touches", since two circles that intersect at two points, would also technically touch.

  • @billa500
    @billa500 Год назад

    Good one👍

  • @Rohit_03
    @Rohit_03 Год назад +1

    Bruh i literally gave this exam and got 18000 rank

  • @alex.n0
    @alex.n0 Год назад

    Nice sir I am preparing for jee exam this year

  • @gone6961
    @gone6961 Год назад +1

    2:55 I m in 9 grade and I was able to solve upto here

  • @N8doggamer
    @N8doggamer Год назад

    Here's one that people got into a heated debacle over:
    Tim can cut through a piece of wood in 5 minutes of time. If Tim were to continue cutting through pieces of wood at this pace, how long would it take him to cut a new wooden piece into three pieces. Some people believe that 10 minutes is the correct answer where as others believe 15 minutes is the correct answer. (The issue here mainly comes down to the wording of the problem.)

    • @carultch
      @carultch Год назад

      I'd say the answer is 10 minutes, and we'd need more information to conclude it is 15 minutes instead. Tim starts with a new piece of wood, and he has to make 2 cuts through it, to end up with 3 pieces of wood. Thus it takes twice the time to make 1 cut, in order to make the 2 cuts and end up with three pieces.
      It didn't specify that whether or not the three pieces add up to the full length (minus the 2 saw kerfs). But since it also didn't specify that he had three pieces plus a scrap piece.

  • @Vishal00567
    @Vishal00567 Год назад +1

    If this was easy then what about hard?

    • @prathamkalgutkar7538
      @prathamkalgutkar7538 Год назад

      Something like this and more :
      If f(x) is a differentiable function and g(x) is a double differentiable function such that |f(x)|≤1 and f'(x)=g(x) . If f2(0)+g2(0)=9 . Prove that there exists some c∈(-3,3) such that g(c).g''(c)

  • @Anmol_Sinha
    @Anmol_Sinha Год назад

    I will be attending this exam next year.. scary

  • @missy1806
    @missy1806 Год назад +2

    I'm confused, I thought the formula for this question is r=(abc)/(√ ((a+b+c) (b+c−a) (c+a−b) (a+b−c))) since we know each side length of the triangle? If this correct the answer r ≈ 1.58 and Prech mentions at 2.25 that BC is the diameter of the circumcircle so therefore r= (√10)/2 ≈ 1.58 so I' don't understand why tangent circles are used regardless if the circumcircle touches the triangle of ABC or am I misinterpreting the question? Imo the radius never changes and the question didn't ask for the different between the radius of both circumcircles or am I wrong and if so can someone please explain why?

    • @tedr.5978
      @tedr.5978 Год назад +2

      I also don't understand what the question means by "touch". Perhaps schools in India use math terms different from the USA?

    • @vincentchen6186
      @vincentchen6186 Год назад +5

      The question is not asking for the radius of the circumcircle, it's asking for the radius of the circle that is tangent to side AB, side AC and the circumcircle.

    • @abhay6576
      @abhay6576 Год назад

      @@tedr.5978 touch aka tangent

    • @redeyexxx1841
      @redeyexxx1841 Год назад +1

      @@tedr.5978 Touch implies the line is a tangent. How is that difficult to understand?

    • @shrankai7285
      @shrankai7285 Год назад

      @@redeyexxx1841 I thought touch meant either tangent or went through AB,AC, and the circumcircle

  • @sulemankhan6409
    @sulemankhan6409 Год назад

    I didn't understand because my geometry is very weak

  • @aadityasharma123
    @aadityasharma123 Год назад

    i gave this paper live.....couldn't solve in time so had to leave it

  • @bebopben2
    @bebopben2 Год назад +4

    Thank you so much! My manager at McDonalds would not move me up to fry chef until I came up with the correct answer.

  • @marcinbednara3825
    @marcinbednara3825 Год назад

    So r is twice the radius of inscribed circle.

  • @RV-hg2fn
    @RV-hg2fn Год назад +2

    Some enlightenment please. Angle BAC is given as pi/2. In other words 3,14 divided by 2 = 1,57 degrees. How did you get to 90 degrees?

    • @shrankai7285
      @shrankai7285 Год назад +1

      cdn-academy.pressidium.com/academy/wp-content/uploads/2021/03/Unit-circle.png

    • @lumina_
      @lumina_ Год назад +3

      pi/2 radians

    • @prathamkalgutkar7538
      @prathamkalgutkar7538 Год назад +3

      Its in radians, 360 degree is 2 Pi Radians

    • @niteshbhargav1728
      @niteshbhargav1728 Год назад +3

      Bro you are in which class 💀💀

  • @SpamSucker
    @SpamSucker Год назад

    I drew this to scale and am having a hard time finding a circle that meets the three points of tangency. In the diagram used, AB is drawn much longer than 1/3 of AC. Something is wrong here, beyond describing segment ME as (r-1.5) rather than (1.5-r) in the diagram at 4:48 (which becomes irrelevant when you expand the terms). I get that the math works, but what is the x,y coordinate of the two-circle point of tangency? Presh can you show this to scale and show where is point D actually in relation to M, and the point of circle tangency? Edit: I guess I can see it now, point T is quite close to point B, and D is indeed below and a little to the right of point M. No follow up needed, I suppose.

  • @QuangGoodman
    @QuangGoodman Год назад

    0:06 r = 1/4 pi
    Damn it, not the closest answer

  • @spoopyd.8910
    @spoopyd.8910 Год назад

    R stands for Racecar

  • @garvitahuja3717
    @garvitahuja3717 Год назад

    This is a very easy ques
    Idk why so many people weren't able to solve it
    I solved it in 2 min

  • @criticgamerz6382
    @criticgamerz6382 Год назад

    Actually Presh! I solved it in a much easier way than yours , we could solve it more easily by considering perpendicular sides as x and y axes.

  • @letstalksciencewithshashwa9527
    @letstalksciencewithshashwa9527 Год назад +1

    bruhhhhhh this is ioqm level

  • @MrEntaroadun
    @MrEntaroadun Год назад +4

    Hardest paper from a university that ain't even in world top 100.

    • @wakeawake2950
      @wakeawake2950 Год назад +2

      Then don't give this exam go to your top 100 University,ooh u can't even solve this 😂

    • @ishansharma3944
      @ishansharma3944 Год назад +1

      IIT Bombay and IIT Delhi are in top 100 engineering Universities.

    • @himanshumech133
      @himanshumech133 Год назад

      @@ishansharma3944 NO ITS NOT

    • @ishansharma3944
      @ishansharma3944 Год назад

      @@himanshumech133 it is, check the qs university rankings of top 100 engineering universities.

    • @sirak_s_nt
      @sirak_s_nt Год назад

      @@wakeawake2950 He might not even be Indian. As a middle class Indian, IIT's are a good to go option and hence its our helplessness that leads us to give this exam (atleast most of us!), many high class Indians literally go to those top 100 universities.

  • @5gallonsofwater495
    @5gallonsofwater495 Год назад

    That is hard. I tried using coordinates and its still hard.

  • @luisandrade2254
    @luisandrade2254 Год назад +1

    If this is an easy problem I wonder what the hard would be

    • @ishansharma3944
      @ishansharma3944 Год назад

      This is why jee advanced is considered the hardest exam for admission to undergraduate engineering. You can find other questions on Google.

    • @prathamkalgutkar7538
      @prathamkalgutkar7538 Год назад +2

      Something like this and more :
      If f(x) is a differentiable function and g(x) is a double differentiable function such that |f(x)|≤1 and f'(x)=g(x) . If f2(0)+g2(0)=9 . Prove that there exists some c∈(-3,3) such that g(c).g''(c)

  • @muroma3088
    @muroma3088 Год назад

    try to say "cicrumcircle" 10 times quickly

  • @scrambledsocks1606
    @scrambledsocks1606 Год назад

    and we are supposed to do it in 2 minutes