Permutations: how do we account for repetitions?

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  • Опубликовано: 27 авг 2014

Комментарии • 58

  • @philipalexopoulos8478
    @philipalexopoulos8478 5 лет назад +133

    This guy is the greatest math teacher on earth

  • @rivertells8876
    @rivertells8876 4 года назад +24

    I am 44 years old and this is the first time I've understood how to work on problems if there are repeating letters

  • @hullgatt
    @hullgatt 5 лет назад +23

    Omg, the relationships are totally blowing my mind. I am rediscovering math with Eddie Woo as my guide and I can see the path so much clearer now. Thank you-WOO! :D

  • @peterdeng8047
    @peterdeng8047 2 года назад +12

    Such a brilliant lecture! Now I am more confident about the exam tomorrow. Big thanks for you, Eddie Woo!!

  • @hunglyo.806
    @hunglyo.806 2 года назад +6

    Loving how confident and vibe when he taught his student. Also, his lecture is really logical and detailed though you felt like you got caught up in the his story,

  • @benjaminarya829
    @benjaminarya829 6 лет назад +1

    Thank you Eddie! You are the best teacher on RUclips

  • @trackmyactivity
    @trackmyactivity 6 лет назад +2

    You are great! Really catch the attention and make it interesting.

  • @varunnagp3903
    @varunnagp3903 8 лет назад +5

    another great lesson, especially the way you explained over counting when there is repetition

  • @raymondzhu6058
    @raymondzhu6058 7 лет назад +22

    thanks so much sir! really hate this topic but you've made it just that wee bit better :)

    • @curryrice9577
      @curryrice9577 7 лет назад +9

      Raymond Zhu
      You mean just that woo better ahaha

    • @saumyojitdas4212
      @saumyojitdas4212 4 года назад

      Kellly
      For one permutation there are extra 5 permutations .
      Why don't we eliminate 5 instead of 6.

    • @hassanrehanfarooq1512
      @hassanrehanfarooq1512 3 года назад

      @@curryrice9577 hahaha

  • @maserekashepherd7484
    @maserekashepherd7484 Год назад +1

    Kelly might never forget anything from this lesson like me

  • @souravmohapatra2501
    @souravmohapatra2501 2 года назад +1

    Best math teacher ever

  • @Anonymous-ox6gd
    @Anonymous-ox6gd 9 месяцев назад

    Excellent explanation, got it crystal clear in my mind now

  • @vedclove
    @vedclove 8 месяцев назад

    Great teacher you are!! Thank You!

  • @negoitamihai8251
    @negoitamihai8251 2 года назад +5

    In an attempt to explain the last part as I was a bit confused too because haven't touched the binomial theorem before permutations/ arrangements. Look up (a+b)^6, that is the equation the KKKLLL(aaabbb) "name" relates to. There is an part of the result of the equation that gives a^3b^3, meaning aaabbb(KKKLLL), where 6 choose 3 "b"'s, where the amount of "b"'s tell us how many items to choose from the lot or 6 permute 6 of the lot gives us 20, the coefficient of the part of the result, and there is the corelation. I haven't looked too much up about this, this is the best I could come up with so I hope it's enough. 😁 You should watch the beggining of his Binomial Theorem playlist atleast for more insight.

    • @jayceel251
      @jayceel251 5 месяцев назад

      Thank you for this! I haven't touched it either (though, I'm sure you have by now 😅) and this made me understand the last bit more!

  • @talhaamin5470
    @talhaamin5470 4 года назад

    Perfectly explained Sir👌

  • @shikhakachroo4290
    @shikhakachroo4290 5 лет назад +1

    Excellent!

  • @subodh4481
    @subodh4481 3 года назад

    Sir you're the most handsome maths teachers I've ever seen and you're the best maths teacher also.

  • @rakshitsingh40
    @rakshitsingh40 Год назад +2

    I am not a maths master and he is awesome and I know that out there they use calculators for calculation which is good but i just wanted to tell that if u asked what's 5! Or 6! Like that in India or even 720 /4 u will be judged as a teacher. I don't say he is bad a teacher good at concepts is far better than a teacher just knowing everything himself or just knowing the numbers... I repeat this teacher is great

    • @jayceel251
      @jayceel251 5 месяцев назад +1

      I think he was asking the class so that he knew they were paying attention and doing the steps along with him

  • @donjour69
    @donjour69 2 года назад +1

    3:34
    Me nodding yes enthusiastically🤓

  • @paulcarello6390
    @paulcarello6390 2 года назад +1

    Picking up from, 6!/[3!(6-3)!] = 6C3. While mathematically correct, the equality is perhaps a little misleading. That being said, 6!/[3!(6-3)!] = 20, which implies that there are 20 distinct permutation of the letters KKKLLL (if we select 6 letters). If we now select 6 letters from the 6 letters (KKKLLL) we will have 6C6 = 1 combination. So, my point is, do not confuse permutations with combinations.

    • @seanmorrison3744
      @seanmorrison3744 2 года назад +1

      No, the equality is correct, because the question is asking for combinations, not permutations. It's 6C3 because the Ls can only go in the blanks left by the Ks. If it were KKKLLLL, the answer would be 7C3=7C4 (both give the same result) for the same reason.

  • @joelg.dampiljr.2757
    @joelg.dampiljr.2757 3 года назад +1

    I never knew that binomial distribution gives a hint about the probability

  • @jacobkaippallimalil2223
    @jacobkaippallimalil2223 4 года назад

    Thanks fort the Video Mr. Woo! I just had a question: suppose from the word KELLY, I picked only two letters e.g KE,KL, etc. Would you approach repetition the same way? Thanks in advance!

  • @karunashirolkar3027
    @karunashirolkar3027 3 года назад

    Beautiful explanation of (a+b)^3

  • @advaykumar4833
    @advaykumar4833 4 года назад +3

    The only video with 0 dislikes.

    • @SMDz
      @SMDz 4 года назад +2

      Just realized that

  • @clintrusselopenia6847
    @clintrusselopenia6847 8 месяцев назад

    Great!

  • @user-rm1jm7pt2f
    @user-rm1jm7pt2f 3 года назад

    I think there is a mistake at 6:57, i mean Ls and Ys can not switch together either it will be a different word so the number of ways the one word can repeat is how many ways can ls switch together plus how many ways can ys switch together not times, it just happened that s factorial plus 2 factorial is equal to two factorial multiplied by two factorial

  • @aleksandermoskov7799
    @aleksandermoskov7799 Год назад

    legend

  • @user-mh9ku4xm6d
    @user-mh9ku4xm6d 3 года назад +1

    i wish you were my teacher 💕

  • @friedrichfermi6559
    @friedrichfermi6559 2 года назад

    thanks sir!

  • @ammaryassereldisoukey8039
    @ammaryassereldisoukey8039 4 года назад

    Hello Mr.Woo
    I have a question regarding the last part about the 2 letter thing
    so im given 6 letters and im asked to to make from it a 2-letter word
    so this is 6!/(6-2)! and then i have repetitions .... im kinda lost
    can you clarify the question of the 2 letter .. i just want to know what was the question
    and thank you in advance for your intuitive videos

  • @dhruvshetty2127
    @dhruvshetty2127 5 лет назад +2

    Shit I ended up learning binomial theorem properly too with this video damn

  • @user-rm1jm7pt2f
    @user-rm1jm7pt2f 3 года назад

    At 8:00 how are u treating words like expressions in bionomial expansions, i mean isn't KKLKLL different from KKKLLL as a word but both are the same as bionomail expansion terms K^3B^3??

  • @saumyojitdas4212
    @saumyojitdas4212 4 года назад

    Kellly
    For one permutation there are extra 5 permutations .
    Why don't we eliminate 5 instead of 6.

    • @norbeex3
      @norbeex3 4 года назад

      You do eliminate 5. If the denominator is 6 than its like you multiply it with 1/6. In other words, you take 1 out of 6.

  • @Eternalshash
    @Eternalshash 9 месяцев назад +1

    why am i not able to apply combinaton on kellyy? can anyone answer

  • @tingchen3114
    @tingchen3114 Год назад +1

    ikr

  • @matthewsmith1571
    @matthewsmith1571 3 года назад

    What does he mean when he says 'overcounted'?

    • @matthewsmith1571
      @matthewsmith1571 3 года назад +5

      nvm...i think i get it. When he says he overcounted, he's referring to the identical permutations that were included

    • @sanjana7053
      @sanjana7053 3 года назад

      @@matthewsmith1571 Exactly he means that we have counted more than they are supposed to be

  • @surjaswetadey1516
    @surjaswetadey1516 6 лет назад

    Sir please help me with this.
    In how many different ways can five boys and five girls sit around a table such that the boys and girls are at alternate positions??

    • @gameswithtags802
      @gameswithtags802 9 месяцев назад

      only 2 ways???

    • @mikelmao.
      @mikelmao. 6 месяцев назад

      ​@@gameswithtags802 that answer is off by 2778 assuming the question states the table is circular 🙂
      with a circular table, we can fix one person in place because the rotation of the table doesn't matter, leaving 9 slots to fill.
      If a boy was fixed in place then there are 4 possible spots to place the remaining 4 boys, which is 4! ways. Then put the 5 girls in the 5 remaining spots, which is 5! ways.
      1x4!x5! = 2800 (total ways)

  • @csabaszekely3098
    @csabaszekely3098 Год назад

    That is Variation and not Permutation!

  • @okthx1759
    @okthx1759 3 года назад

    I still didn't understand this sir,can anyone please explain me in the comments
    PLEASE,BEGGING YOU because I am currently breaking down cuz I am not able to umderstand anything

    • @sanjana7053
      @sanjana7053 3 года назад

      Take the eg.Kelly, here, out of 5 letters i need to arrange 5 letter, therefore i can arrange them in 5P5 ways. But also there are two identical letters (i.e. L and L). So even if we arrange them in different ways they word is same. Those L's can arrange themselves in 2P2 ways = 2! ways = 2 ways. (1st L, 2nd L or 2nd L, 1st). which is the same. So we divide 5P5 by 2! to get number of ways to arrange the letters.

    • @sanjana7053
      @sanjana7053 3 года назад

      Hope you understood. And see the vid again