What does a ≡ b (mod n) mean? Basic Modular Arithmetic, Congruence

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  • Опубликовано: 26 ноя 2024

Комментарии • 424

  • @blackpenredpen
    @blackpenredpen  6 лет назад +357

    What donuts are those?

  • @bakirhaljevac3584
    @bakirhaljevac3584 4 года назад +546

    It took you around 3 minutes to say what I needed to know, the same thing that my professor unsuccessfully tried to explain in one hour. Thank you so much

    • @v-neko8074
      @v-neko8074 3 года назад +1

      same

    • @tristanfan4741
      @tristanfan4741 3 года назад +9

      so fucking dmn right

    • @finghinmccarthy5021
      @finghinmccarthy5021 3 года назад +1

      True

    • @JuuzouRCS
      @JuuzouRCS 3 года назад

      True. I am right now going through the same experience.

    • @shreyas_._
      @shreyas_._ 2 года назад +2

      I wonder which professor took one hour for congruence 😅then for sure your whole syllabus time schedule gonna wasted..., ഒരു മയത്തിൽ ഒക്കെ ആവം കേട്ടോ ...

  • @johnlara1365
    @johnlara1365 5 лет назад +157

    I am a senior math and CS major, I have used modulo almost as much as I’ve used pi and I have always been confused by congruency. No one has been able to explain congruency more clearly and digestible than you. Thank you!

    • @dominicellis1867
      @dominicellis1867 Год назад +6

      Basically you throw out the quotient and keep the remainder. It's periodic math like the roots of a trig function.

  • @GraceJoe-u6y
    @GraceJoe-u6y 7 месяцев назад +8

    I watch 7 videos of about 20 minutes about modular arithmetic and didn’t understand anything but your 6 minutes video made me understand. I don’t know what to say

  • @rainyday4709
    @rainyday4709 2 года назад +13

    30min trying to understand this congruence with my book .
    And this man make me understand it just in 1:46 seconds
    I wanna cry .
    Why professor make life complicated whyyy ...
    THANK YOU SO MUCH.
    I really respect you 🙏🙏

  • @v-neko8074
    @v-neko8074 3 года назад +127

    Some teachers in universities: 2h lecture
    blacklenredpen: 6minutes

    • @davidbrisbane7206
      @davidbrisbane7206 3 года назад +2

      Too right mate, plus we can repay bprp's videos as often as we like.

    • @mohammedhussain6749
      @mohammedhussain6749 3 года назад +3

      He is just explaining the procedure not the theory, origins or proof

    • @EulerJr_
      @EulerJr_ 3 года назад +2

      @@aymenchamia7470
      I do, and he is 100% right.
      Our lecturer is extremely smart and knowledgeable no doubt, but he just can’t explain the procedures and concepts in a simple enough way for anyone to understand.

  • @sergioh5515
    @sergioh5515 6 лет назад +175

    PLEASE MORE MODULAR ARITHMETIC! You're the best

  • @meccamiles7816
    @meccamiles7816 5 лет назад +18

    Your ability to change the marker you’re writing with so fast is amazing...

    • @krimzonghost1987
      @krimzonghost1987 4 года назад +1

      I read this comment and watched the video again just because of this. lmao. Wow! You were not joking.

  • @yon1623
    @yon1623 Год назад +2

    I spent an hour trying to understand it from my book... 6 minute video is what i needed.

  • @billofrights5064
    @billofrights5064 6 лет назад +72

    When I took abstract algebra, I found
    a ≡ b (mod n) quite confusing. The meaning seems to be
    a (mod n) = b (mod n), but equivalence must mean more than this.

  • @arnasvaicekauskas7693
    @arnasvaicekauskas7693 6 лет назад +463

    Why is this video 2Pi minutes long ?

  • @barence321
    @barence321 2 года назад +4

    In Beachy 4th Ed., the authors write " a ≡ b (mod n) if and only if n|(a - b)." The proof goes in both directions, so you see that n|(a -b) does indeed show that a/n and b/n have the same remainder. I just finished going over this proof again for my abstract algebra class. Very simple when you do the proof both ways.

  • @roof310
    @roof310 Год назад +5

    (by wikipaedia) Actually, the first claim is the most correct one, same remainder when a and b are divided by n,
    a = kn + r, b = jn + r then we have a - b = (k-j)n + 0 which means that n | a - b (the last claim). If we add b to both side,
    a = Kn + b by setting K = k - j.
    edit: depends on variables to choose the most suitable one.

  • @Jack-cm5ch
    @Jack-cm5ch 6 лет назад +50

    Omg saving my grade once again. God bless you. Wish you had a patreon...

    • @Wannabesage336
      @Wannabesage336 5 лет назад +7

      For those of you watching this in the future:
      He does!
      www.patreon.com/blackpenredpen

  • @azure3544
    @azure3544 5 лет назад +6

    I learned more from this guy than from my entire math class xDDD
    My math teacher made this look like rocket science...

  • @Mindmodic
    @Mindmodic 4 года назад +1

    Finally I've been looking for a decent explanation for this for about an hour! Years ago when I was in school we never learned this and 'remainder' was only referred to when you were doing sums by hand, the remainder would be the next 10, 100 or 1000 etc. from your addition, I didn't see it as any other sense!

  • @UnathiGX
    @UnathiGX 6 лет назад +6

    This is by far the best explanation....IMO!...here I come....!!!!

  • @juandelacruz9125
    @juandelacruz9125 6 лет назад +3

    Thanks blackpenredpen for teaching us this!

  • @bgbg418
    @bgbg418 3 года назад +1

    Wow I wish I found this in my first year. It would've saved me hours of lengthy abstract examples and confusion. Why do universities make things so unnecessarily complicated sometimes 🙄.

  • @WSUFan2017
    @WSUFan2017 6 лет назад +49

    You should do more number theory, especially stuff like Euler’s totient function (since it’s my favorite subject ;D)!

    • @blackpenredpen
      @blackpenredpen  6 лет назад +4

      I will. In the meantime, you can check out Max's videos here: ruclips.net/channel/UCP-ZCMz7olJPUI78b_bQrvQvideos?disable_polymer=1

  • @krimzonghost1987
    @krimzonghost1987 4 года назад +1

    C# exercises led me here... and I ain't even mad. Awesome video!

  • @michelletan7855
    @michelletan7855 3 года назад +1

    thank you so much! you are amazing to explain the modular arithmetic! thank you thank you!

  • @jihyepark9139
    @jihyepark9139 5 лет назад +1

    Our major instructor discussed this topic like using speed of light.... Boom finish!!

  • @vegetaiv9275
    @vegetaiv9275 Год назад

    Your explanation is amazing. It is way better than my professor's! Thank you so much!

  • @sazsaiglesias
    @sazsaiglesias 2 года назад

    you saved my exam tomorrow..thank you

  • @zellpeppers8181
    @zellpeppers8181 Год назад +1

    thankyou so much!! this really helped a lot 🥰🥰

  • @arandomguy9518
    @arandomguy9518 3 года назад +3

    Got what I needed by 0:59 ...mad thanks 👍

  • @Surya_Kiran_K
    @Surya_Kiran_K Год назад +1

    I would attend every class of this guy 😭👍💓

  • @jgz919
    @jgz919 Год назад

    Thanks for the refresher. I hardly understood this when getting my undergrad degree and now that im working on my masters it came back to haunt me 🤣

  • @abuhanifhanif3636
    @abuhanifhanif3636 5 лет назад +1

    Thanks a lot from Bangladesh

  • @aayushve426
    @aayushve426 7 месяцев назад +1

    Great video as always !

  • @nithin8432
    @nithin8432 3 года назад +4

    just had a great and clear understanding this was the lecture i needed thanks a lot mate!!!

  • @faizzailan5936
    @faizzailan5936 3 года назад

    this is the best number theory explanation, well done

  • @erickarbieto8111
    @erickarbieto8111 4 года назад +1

    Eres un crack! Y todo lo digo en español, porque hasta en Latinoamerica disfrutamos de tus videos; en serio, aprendo muchísimo! Thank you!

  • @militantpacifist4087
    @militantpacifist4087 2 года назад +1

    This video has the most epic donut-math intro to be honest.

  • @ayyagarisrinivas5082
    @ayyagarisrinivas5082 4 года назад +1

    Helpful man thanks ; )

  • @shady153
    @shady153 Год назад

    This video was awesome! I'm so glad I found your channel. You have a new subscriber here.

  • @scar6073
    @scar6073 Год назад

    Thank you for explaining this in a straightforward manner, I FUCKING LOVE YOU!

  • @ZectonplaysMC
    @ZectonplaysMC 5 лет назад +1

    Dude i normally watch ur vids for fun but now i actually need help and i come back to ur channel😂

  • @madhurimamohanty2867
    @madhurimamohanty2867 3 года назад +1

    Well in India there's an exam called NMTC where you have to learn this as a part of syllabus when you're in grade 6. By the way I'm of grade 6 and I enjoy watching your calculus lectures

  • @shacharh5470
    @shacharh5470 6 лет назад

    Congruence relations and their corresponding quotient sets (and groups, and spaces, etc) are some of the richest topics in maths, and modular congruence is one of the most useful and ubiquitous ones.

  • @prestontao2
    @prestontao2 3 года назад

    thanks this helped me pass my test

  • @adhiyanthaprabhujeyashanka2091

    At @4:17 you said it is two on the left hand side, but it is actually 10, just a small error, but adds more value to your content if you take care to correct, between everything is clear sir 🔥🙏

  • @ryanziller220
    @ryanziller220 2 года назад

    I can guarantee that most people will confuse the activity shown as comparable to developing a conceptual understanding of modular congruence. If he provided any sort of discovery in which one could find the relativity of discrete mathematics while performing the procedures of modular arithmetics then we could satisfy the looming problem of: When and where have I seen this before? Instead, as is the case of 'cutting corners', he stressed his strategic competency while disregarding the importance of the methodical alternatives represented. Those people whom hate maths or find the language nonsensical and deceptive do so because oftentimes someone who is still learning to teach the subject(s) denotes pertinent information yet fails to instruct on the basis of that which is the significance of an ontology; implying that, the concepts which are introduced can be conferred to the relevancy of an instantaneous appreciation by others. Per inference, everyone not exploring a career as a mathematician is ignoring the facts of exercises of the discipline. Why teach math while you are not becoming a mathematician?

  • @BentHestad
    @BentHestad 3 года назад +2

    Very helpful! Thanks!!

  • @motivationalcomred
    @motivationalcomred Год назад

    summary: a = b mod m is known ads congrunce relation where a divides m and b divides m with same remainder and a is some constant times *m +b

  • @ghassanabdalsalam9938
    @ghassanabdalsalam9938 2 года назад +1

    thaaaaaaaaaaaaank you , amazing , I love your explanation

  • @Amanupadhyay-po6ls
    @Amanupadhyay-po6ls 2 года назад

    Great Explaination sir 👍
    11 grade student fom India

  • @liamcauquil6800
    @liamcauquil6800 5 лет назад +8

    Hey, good video! Could you explain how 10 ≡ -2 became 10 ≡ 2 by adding 4 to the -2?

    • @liitutereuiui4687
      @liitutereuiui4687 3 года назад +1

      I also want to know

    • @Nour_Ayasrah
      @Nour_Ayasrah 3 года назад +4

      too late, but if by any chance someone needs it later on, this is one way to think about it.
      note that if you are dealing with mod(n), any integer will be congruent to the set starting from 0 to n-1(i.e: {0,1,2,...,n-1}), so for mod(4) we have {0,1,2,3}, so now what happens if we add "4" or multiples of it to any of these? well, u go a full cycle/s so 0+4 = 0 mod(4), 1 + 2*4 = 1 mod(4) etc.
      so essentially inside the realm of mod(4) adding 4 is analogous to adding 0 in the normal arithmetic, does not change a thing. so -2 mod(4) = -2+4 mod(4) = 2 mod(4).

    • @azharuddin7013
      @azharuddin7013 3 года назад

      @@Nour_Ayasrah when he says that 10 is congruent to 2 mod(4) but that cannot be according to the first definition because 10 and 2 does'nt have same remainders.Plz help

    • @Nour_Ayasrah
      @Nour_Ayasrah 3 года назад +5

      @@azharuddin7013 hey buddy, the first definition says that both numbers have the same remainder when divided by n, and that is true here.
      2/4 = 0*4 + 2(this 2 here is the remainder)
      10/4 = 2*4 + 2(again this is the remainder)
      since in both cases the remainder is 2, they are congruent

  • @jeremyjakob9721
    @jeremyjakob9721 4 года назад

    These are all essential notions for how modular arithmetic works, but perhaps misses at the heart of what is happening. Modular arithmetic by virtue of being "modular " means that there is some equivalence relation on the integers in Z. Z mod n can be viewed as the quotient map from Z to the set of elements partitioned by the equivalence relation "a is congruent to b mod n if (a-b) divides n or equivalently if a is congruent to kn +b. That is Z mod n partitions Z into "equivalence classes" defined by the above relations. This more general approach allows for better understanding of the role that modular arithmetic plays in both group and ring theory.

  • @thundrking
    @thundrking 5 лет назад

    Straight to the point.. thanks

  • @tcpudp1429
    @tcpudp1429 2 года назад

    I just want to say thank you man, you really helped me out
    😃

  • @GreeeenT
    @GreeeenT 6 лет назад +15

    do you have my schedule or something ?? how do you always upload what I need. thanks man !

  • @manojrajguru8852
    @manojrajguru8852 6 лет назад

    u are the best professor..

  • @giantdad7
    @giantdad7 6 лет назад +4

    Please keep uploading Number Theory videos!

  • @avatarmh
    @avatarmh 4 года назад

    This guy nailed it. However, you might like to think about congruence, blackpenredpen covered it. Clarifying and memorable. Now I can move onto some proofs that have been baffling me!

  • @masongkhun5292
    @masongkhun5292 5 лет назад

    Hey bro ! Maybe I’m the latest one for this video but I want you to solve a math problem
    Here it is!
    Prove that: 1•3•5•...•2013+2•4•6•....•2014 is a multiple of 2015
    I hope you see my comment and solve it for me. Thank you !

  • @michelle732mn
    @michelle732mn 3 года назад +1

    THANK YOUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU!
    P.S. I laughed when you said mod 1 kills all the math lol

  • @dmshot48
    @dmshot48 7 месяцев назад +1

    Killing all the numbers you eat😂

  • @navster100
    @navster100 4 года назад +6

    im doing proofs with modular congruence and my head is exploding

  • @nnnmmiiii6994
    @nnnmmiiii6994 2 года назад

    excellent explanation

  • @oborooizamisi1894
    @oborooizamisi1894 2 года назад

    Amazing explanation, just what I needed

  • @frankensteinapps9442
    @frankensteinapps9442 2 года назад +1

    Thanks man I was bit confused in equivalence relations when this came up , turns out I was interpreting it in a wrong way

  • @woojason7119
    @woojason7119 4 года назад

    thanks for your vdo you saved me from an algorithm course
    it looked me quite a long time to understand what is meant by a=b (mod n)

  • @nathanielgabriel
    @nathanielgabriel 5 лет назад

    Smooth explanation

  • @MathForLife
    @MathForLife 6 лет назад +78

    Ahah, "killing all math":DDD

    • @blackpenredpen
      @blackpenredpen  6 лет назад +3

      Eightc yup!!!!

    • @blackpenredpen
      @blackpenredpen  6 лет назад +5

      And max, you can record an intro and send it to me via google drive so I can put it in my videos to let more ppl know about ur channel.

    • @MathForLife
      @MathForLife 6 лет назад +3

      blackpenredpen thanks!!

  • @robertkissinger6050
    @robertkissinger6050 4 года назад

    Excellent explanation!

  • @Gold161803
    @Gold161803 6 лет назад

    I have actually seen (mod 1) used. It was to denote the fractional part of a non-integer, but non-integers aren't being considered here

  • @AnayBhad
    @AnayBhad Год назад

    thanks for this video helped me a lot.

  • @sergioh5515
    @sergioh5515 6 лет назад +1

    You make math so entertaining :)

  • @zhangruoran
    @zhangruoran 5 лет назад +10

    : D this is exactly what I taught my students.

  • @Ethan-mj6wy
    @Ethan-mj6wy 6 лет назад +3

    Great video, loving all the number theory :)

  • @lucasgparker
    @lucasgparker 6 лет назад

    Congrats on the 100k!!

  • @123luckeyman123
    @123luckeyman123 3 года назад

    This is really helpful! Where is the number Theory section in your channel

  • @AlgyCuber
    @AlgyCuber 6 лет назад +29

    H times i factorial

  • @WhiteDotX
    @WhiteDotX 6 лет назад +21

    I just keeping learning a lot from you.
    Greetings from Mexico!
    Can you talk about set theory or keep doing number theory?

    • @blackpenredpen
      @blackpenredpen  6 лет назад +2

      Silvestre Frijol Cruz thank you!! I will focus on number theory, probability and combinatorics and calc.

  • @Ebvardh
    @Ebvardh 6 лет назад

    Lovely explanation. Helped me finally visualize this concept before you even did the examples.

  • @mahadhersi3754
    @mahadhersi3754 3 года назад

    Thank you professor BlackpenRedpen I appreciate you this amazing lesson.

  • @azharuddin7013
    @azharuddin7013 3 года назад +2

    @blackpenredpen Hi,
    when you say that 10 is congruent to 2 mod(4) but that cannot be according to the first definition because 10 and 2 doesn't have same remainders.Plz help

    • @gototcm
      @gototcm 2 года назад

      Actually, they do. 10 divided by 4 is 2 with a remainder of 2. 2 divided by 4 is zero with a remainder of 2. Hope this helps.

  • @prestontao2
    @prestontao2 3 года назад

    i just realized he used a blue pen. this is beyond science

  • @dikshabhise7480
    @dikshabhise7480 3 года назад

    great teaching🥰 I finally understand 👍

  • @utkarshraj3272
    @utkarshraj3272 4 года назад

    You are great.
    Thank You Very Much

  • @valentinejepkemei149
    @valentinejepkemei149 3 года назад

    Thank you you are talented keep it up good work

  • @MathsOnlineVideos
    @MathsOnlineVideos 3 года назад

    Thanks a lot man. That helps a lot!

  • @thimirabandara679
    @thimirabandara679 4 года назад

    very good video and very good explanation!

  • @ayeshajavediqbal3994
    @ayeshajavediqbal3994 4 года назад

    Waoo nice one lecture👍😊

  • @collin2628
    @collin2628 4 года назад

    thank you mr. pen

  • @ignite21385
    @ignite21385 4 года назад

    This equation was everything.

  • @AhmedAzhad
    @AhmedAzhad 4 года назад

    Thank you very much. Very well explained.

  • @elijahseh7112
    @elijahseh7112 5 лет назад

    Can you please do a video on multiplicative inverse modular arithmetic? I fully understand the basic modular arithmetic but finding the multiplicative inverse in modular arithmetic just keeps going over my head!

  • @GeorgeDCowley
    @GeorgeDCowley 4 года назад

    Thanks for telling me that the brackets were important.
    I was just subtracting.

  • @Phelly2
    @Phelly2 5 лет назад +21

    What the heck are you holding? A microphone? It looks like a psionic amplifier from the game System Shock 2. lol

  • @antoinelunaire9462
    @antoinelunaire9462 4 года назад

    Thanks a lot, brief and effective

  • @itzmrinyy7484
    @itzmrinyy7484 5 месяцев назад

    Thank you so mucj for this video! I was just watching an IMO prpblem solving video and i couldn't help but wonder what "mod(n)" meant.

  • @psrs985
    @psrs985 2 года назад +1

    Mom I'm becoming a mathematician

  • @jerrytsai9580
    @jerrytsai9580 4 года назад

    Very well explained. Thank you so much.

  • @shreenidhhi8633
    @shreenidhhi8633 4 года назад +1

    I have a doubt.
    From a=(k×n)+b
    Can we say this is similar to
    dividend =divisor × quotient +remainder

  • @letoheeo3970
    @letoheeo3970 4 года назад

    Best explanation ❤️❤️

  • @KidGamerTV2024
    @KidGamerTV2024 6 месяцев назад +1

    When i first saw a and b in math i thought a and b meant 1 and 2

  • @danieljohannbutcher9927
    @danieljohannbutcher9927 4 года назад +1

    The black ball looks like a prop from the movie parallel. Great explanation, weird microphone.