Time Speed and Distance 8 | (Escalators contd) CAT 2024 | Arithmetic | Quantitative Aptitude
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- Опубликовано: 10 апр 2019
- CAT PREPARATION 2024 I QUANTITATIVE APTITUDE PREPARATION for CAT 2024
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@@pavithran5515 100000
In the question of the Shopping Mall escalator floor 1 to 5: I expected another approach which would be realizing that the speeds under the given conditions are always in AP (M+E, M, M-E), so the time taken under the circumstances will be in HP and the answer will be the harmonic mean of the given time values.
You are right we get same answer by that approach
Yes.
@@akshaychavan4673 how can we know that the speeds are in AP?
even in the last question the HP method could be used?
@@venumohan5500from info given in question it is of the form---m-e,m,m+e (a.p)
Refer previous video(7th part)
Thank you so much Sir.. You don't know how relieved I am .. I always felt uneasy in this topic..But now I am confident about getting it right
Ravi Sir is the saviour for all of us! Please dont forget to like all his videos as and when you play them!
Although the last question was a little challenging, I was able to solve that on my own. Thanks Ravi Sir for explaining this concept so nicely.
Thank you sir for all the hardwork you have done for all of us.
Thank you sir for all the efforts. 🙏
Best very best ...I am already taking coaching bhit still I came around your vedio and find very very much helpful...after spending 50 k in coaching center its wast of money ...your explanation is best
I Like how your channel name is You as after reading your comment I felt that I did the same mistake as well.
Thank you so much sir for clearing the concept 👍👍
Sir, Very nice concept ❤️
It was very help full sir keep going
In last ques n=15 b took 8 step so remaining steps are 7 which are taken by escalator so
It will be e*tb=7
Similarly for c remaining steps are 10
So e*tc=10
By equating we get tb:tc=7:10
Alternate way to solve Q1:
Speed of P in case 1 = 25 steps / 30 sec = 5/6 steps/sec
Speed of escalator = e (let)
Thus, (5/6 + e)x(30) = N [speed x time = dist]
Speed of P in case 2 = 5/2 steps/sec (since it is tripled)
So: (5/2 + e)x(18) = N
Equate and solve for e….. turns out e = 5/3 steps/sec
Put e in any one of the above 2 eqns to get N = 75 steps.
Sir.....!
Thank you so very much❤
GREAT VIDEO
nice good concepts sir
Thank you so much SIR
Thank you sir for videos .
Thank you sir .
Thankyou,sir.
thank you sir🙏
Solved the 5:57 question by AP & HP method,
Speed can be considered M+E, M, M-E for time 36sec, ? , 108sec , since speeds are in AP, time will be in HP so the time when escalator is not moving can be calculated by b=2ac/a+c . Answer is also same (54secs)
is this also correct?
Yes CORRECT
Thankyou 💜 so much sir 🙏🏻
how do u got those 36,108?
Thanku sir
The shopping mall question could have been done in 2s by HP concept
Hey !
I was trying the same thing, yet failed. Would you share the solution using the hp concept ?
@@niloychakravorty3832 M+E ,M ,M-E are the speeds and they are in AP., therefore their time is in HP . now T {M+E}= 36
T{M-E} = 108 , Therefore T{M} = 2*36*108 / 36+108 = 54
Thank you so much @avinash.
The H.P concept has made all these problems a piece of cake, I would earlier try to use relative speeds and then stare at my notebook looking to reduce that one extra variable.
can u tell me how ?
Thanks uhh sir jii❤❤❤❤❤
While taking time which is distance/speed, the speed we have to consider will be relative speed or A's speed alone?
17:47 how much steps will taken by b ? I did like this
Steps taken by A =25+25E/3 and B=20+10E by solving this i am getting E= 11/3 and putting 11/3 in equation of A giving 50 steps but B giving 56.66 steps . But according to sir if you will put the value in b you are getting same steps.? How
YOU HAVE CALCULATED WRONG IT WILL NOT COME 11/3
for the second question i am getting answer by applying AP and HP method
in second question time is in hp we can easily solve using hp formula aslo
Hi Sir, I have a doubt. In the last question, why have we not considered the relative speed (x-e) but just x when put it equal to (10/ta) in A white moving up or down for that matter?
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In Some videos u have talked about the quizzes can u plz tell me where can i find them ??
e/x in last question will be 1. 30-10=20
No yaar it's 1/2
In the question with A and B moving together,
A takes 25 steps to reach the top while B takes only 20.
But we have taken speed as A= 3x/second and B=2x per .
Ideally, higher is the speed, time taken should be lesser right?
Is this the right approach?
Yes, the approach is right. The case you have mentioned is when 'D' is constant, here the distance or steps taken by A and B are different.
So, when escalator is switched off N(A)= 50 and N(B)= 60 which means B would have already taken 10 steps before A walked up in escalator that's why even though their steps ratio was 3:2 B reached early to the top.
Not given that they walked up on escalator together.
hope this ans will help you.
@@swatibisht4572 oh. Clear now! :) Thanks a ton
@@jahnavijayaprakash9643 ☺️
@@swatibisht4572
N = 50 for both A and B. (From your comment, N(B)=60 is incorrect.)
Therefore, B did not get a head start.
Even if 'D' is constant and they start together, the person with higher speed (A in this case) will always climb more steps.
E.g.
A → 3 steps/sec
B → 2 steps/sec
E --> 1 step/sec (constant, same for both A and B)
N = Time x Effective speed (A+E or B+E)
A x Time for A = Steps covered by A
B x Time for B= Steps covered by B
E x Time for A or B = Steps covered by E with A or B
Substitute any value of D (i.e., Number of steps), e.g., N = 12, 24, 48 etc, the number of steps taken by A will always be greater than B (even though time taken by A to reach the top will be less) because speed of A is greater than B, and E is same for both of them.
The confusion arises if you misinterpret 3 steps/sec as 1 hop for A. (And 2 steps/sec as 1 hop for B)
Ofcourse, if we were to consider hops, A will hop fewer times than B to reach the top. But if we consider steps/sec, 3 steps/sec literally and mathematically means the person has climbed 3 steps in 1 sec (even though A might have skipped 2 steps and hopped onto the 3rd step).
2nd question can also be solved by AM HM concept easily
In shopping mall question if we use AP, HP concept ,we can solve that question within 1 min.
9:48 10:36 ⭐
For last question...I took hp of A which gives no of steps...
HP wala funda is way quicker than equating for some question.
if N is no of step when it is switched off then why do we write the equation of N = no of man step + escalator step. Logically it shouldn't be this then ?
Q2. Can be solved with HM formula
@15:27 , can the ratio of time also be taken as 2:3 to solve the ques?
No because distance covered by them is not constant, we can use that only when D is const
Why speed of a is taken as 3x?
Why Cant we just take time as inverse of speeds like speed is in ratio 3:2 then time should be in ratio 2:3 in second last question?
Because distance is not constant. While the Total distance i.e.the no.of steps on escalator is constant, individually A and B don't cover equal distances
In 15:51, You have multiplied time taken by A to speed of escalator. I can't understand this
If the speed of escalator is not given we take with time given multiple by E but here time is also not given that's why we have 25/3x
Thankyou sir
Is there any other method of solving the last question.
I am bit confused in the last question..
Its good. Learn this.
Sir , shopping complex 1st to 5th question , can we just use harmonic mean thingy
Yes
Can u please tell how ?
@@kunalsingh6423 Instead of using Harmonic you can go with AP method by using effective speed funda. Take speeds as M/36 +1, M/t , M/108-1. These three speeds are in AP. Calculate difference between M/36-1 and M/108-1 and divide it by 2. Add this difference to M/108 -1 and equate to M/t. You will get 54 seconds.
@@kunalsingh6423
3 speeds - M+E, M, M-E are in A.P. since their common difference is E.
Therefore, the time taken will be in HP.
So, the HM of the 3 quantities will be - 2ab/a+b.
Solve and you'll get the answer.
All the best
Yes
In the second last question, where A and B are moving up escalator why have we taken their speed to be 3x:2x. Why do we require x when we know the exact quantity?
If you listen carefully , 3:2 is tge ratio of speeds not the speed themselves so 3x and 2x .
A takes 3 steps for every 2 of B's steps which means if B takes 4 steps, A will take 6 steps and similarly if B 6 steps then A 9 steps. So we only know their ratio not the actual values.
Sir, 17:40 why the RATIO OF a:b is not = 2:3 ?
When A takes 3 steps B takes 2 steps
A- 3steps ; B- 2steps
A- 6steps; B- 4steps
.
.
.
.
.
@@aayushdeo9143 I'm also saying the same thing 3 steps of A = 2 steps of B. Therefore A/B = 2/3
@@pritheshnarang2166 I think you are not applying ratios correctly, here we are looking for the speed ratios of A & B.
40/x kaise??
Please help with this question sir
Pavan walked up a descending escalator (a moving staircase) and took 154 steps in 100 seconds to reach the top. Rishabh started simultaneously from the top and taking 3 steps for every 4 taken by Pavan, reached the bottom in 40 seconds. How many steps from the bottom were Pavan and Rishabh, when they crossed each other?
Total steps = N
Speed of escalator = e
ratio of PAWAN Speed to ratio of RISHAB'S is 4:3
SAY Pawan's speed = 4x
Rishab's speed = 3x
Overall effective time taken for total steps 'N':
Case 1: (Pawan and escalator in opp. direction) N/(4x - e) =100 ...1 (Pawan- upwards)
Case 2: (Rishab and escalator in same. direction) N/(3x+e) = 40 .....2 (Rishab- downwards)
we know Pawan took 100s to take 154steps ...hence pawan speed,4x = 154/100
x =77/200
Solving 1 and 2 by x value, we get N = 77 and e = 77/100
they will cross each other after (total distance /individual speeds) secs
i.e., 77/(4x+3x) seconds, i.e., 200/7 seconds
Number of steps from bottom = (4x-e) *200/7 = 22 steps
Number of steps from top = (3x + e) *200/7 = 55 steps
How 25/3xE-20/2xE =5/3xE🤨🤨???
Same doubt
Sir.....last Question me ik ratio nikala hai yeslea tb & tc consider kia hai......but sir agar ( 8 / tb ) & ( 5/ tc ) lekar solve karne par mera answer same ni aa raha......mujhe bas reason jaana tha aisa kyu ho raha hai 😭
damn, same
nvm I got it. Inke steps same nahi hai B ke 8 and C ke 5. THerefore, Distance is not contant, hence if speed is 16:7, time cannot be 7:16. For time of B, divide no of steps(8) by speed (16) and same for C. The answer will be 7:10
Sir for the last question, tb:tc is 7:16 not 7:10, I even checked the answer, 7:16 is the crct one.....
Explain how?
Ya, 7:10 is actually the ratio of the number of steps taken by escalator in B and C's case.
@@shreyamishra5447 Both ratio would be equal to 7 : 10 beause speed of the escalator is constant.
No. Answer is 7:10
7:16 is the ratio of speed taken by C and B, 7:10 is the ratio of time taken by B and C.
last question is not good for my brain
Sir video lectures are very helpful..thankyou so much for clearing our concepts
But can you just change or mute the starting sound of the lectures ,it is very much annoying while using the earphones.
or you can just mute it for 30 seconds or skip it!
Like realllyyy?? xD
Banda apna intro bhi na chalaye? 😂