AMC 8 Math Class 2 - Casework,Complementary Counting,and OverCounting(PIE)

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  • Опубликовано: 24 окт 2024

Комментарии • 111

  • @eden409
    @eden409 8 месяцев назад +1

    your teaching methods and your techniques are so easy to understand and effective. this wasn’t really the feeling I got in paid tutoring. thank you so much!

    • @SohilRathi
      @SohilRathi  8 месяцев назад

      Thanks, glad to hear that 🙂

    • @austins.7034
      @austins.7034 4 месяца назад +1

      @@SohilRathi you inspire me to do my best every single day.

  • @joy_chen
    @joy_chen 2 года назад +6

    Thank you so much for these videos ~ You explain very cleary!

  • @h.pandya7107
    @h.pandya7107 4 года назад +8

    this complementary counting was way too good. I have been doing AMC myself and finally I found a channel that substitutes for an institute

  • @QUXx.
    @QUXx. 9 месяцев назад +1

    This helped me alot I was stuck on that question for a long time

  • @h.pandya7107
    @h.pandya7107 4 года назад +13

    BRUH this video taught me such an important concept i really appreciate this thank you so much I did the past exams and got like average of 23 with your channel this can be a 25 thank you so much continue making videos!

    • @Notaarav6876
      @Notaarav6876 4 месяца назад

      Bro how do you get 23. That is a very high score.

  • @MichelleOkonji
    @MichelleOkonji 4 месяца назад +1

    hello sohil rathi. im trying to prepare for a different competion. this is really helpful
    😃

  • @ThanhNguyen-oj2dt
    @ThanhNguyen-oj2dt 4 года назад +3

    For q4 mrs jones - if one family brings dishes 1,2,3 and the second family brings dishes 4,5,6 doesn't this mean the third family can only bring dishes 7,8 which is only 2 rather than 3 dishes?

    • @SohilRathi
      @SohilRathi  4 года назад +3

      Hello, the question states that no two families can bring the same combinations of 2 dishes. For example, a family could bring 1,2,3 and another family could bring 1,2,4 and that would be ok since they don't have the same exact 3 dishes.

  • @imfrommars7362
    @imfrommars7362 Год назад +1

    Why do you divide by 2 factorial in question 6 of the homework. Can u please explain? Thanks

    • @SohilRathi
      @SohilRathi  Год назад +1

      2 T's have 2 ways of being arranged, but they are the same arrangement. Also, you can see this by the word arrangement formula.

    • @imfrommars7362
      @imfrommars7362 Год назад

      @@SohilRathi Oh, ok, thank you 🙏

  • @wenwenstudios6755
    @wenwenstudios6755 3 года назад +5

    Thank you so much for these AMC preparation videos! They are helping me a lot. I subscribed.

  • @mayleespann4552
    @mayleespann4552 4 года назад +9

    Thanks Sohil. You explained the concepts better than my college math teacher, no joke!

  • @Nvxd1
    @Nvxd1 2 года назад +2

    Thank you so much!

  • @nm-to9py
    @nm-to9py 4 года назад +12

    You're going to go far in life. Great work!

  • @h.pandya7107
    @h.pandya7107 4 года назад +5

    good channel i'm preparing for amc this channe's helpful

  • @Mythxc_Memes
    @Mythxc_Memes 9 месяцев назад

    I'm a bit confused about 51:33 When would you have subtracted it 3 times? I don't know if this is a stupid question but...anyway thanks for the content! Just subbed :)

    • @SohilRathi
      @SohilRathi  9 месяцев назад

      That is how PIE works. Let's focus on the common section where the three grandkids G1&G2&G3 all call. We add the days when G1 calls, G2 calls, G3 calls which includes that section 3 times, then subtract the days when G1&G2 call, the days when G1&G3 call, and the days when G2&G3 call, which subtracts that area 3 times. So we need to add that section back when G1, G2, G3 all call.

  • @MiteshVaria
    @MiteshVaria 26 дней назад

    amc 2015 middle school 8 problem - since each team plays each other twice - then total number of games will be 112 because each team will play 7 other teams twice - which means each team will play 14 games. 8 teams times 14 games = 112 games SOOO final answer should be 112 plus 32 = 144!!! please check

    • @SohilRathi
      @SohilRathi  25 дней назад

      Yes, each team is playing 7 other teams twice, but then we are doublecounting the games (A plays B, is the same as B plays A). That is why we need to do (8 choose 2) to get the team pairs for games, then multiply by 2 (since they play each other twice).
      (8 choose 2) = 28 x 2 = 56 total games within the conference. Now add 8 x 4 = 32 games outside the conference to get 88.

  • @hassiumhelium1404
    @hassiumhelium1404 6 месяцев назад

    In the mastering amc 8 book chapter 2 combinations numbers 2.4.2 and 2.4.5 are the same

    • @SohilRathi
      @SohilRathi  6 месяцев назад

      Thanks for letting me know. I have removed the duplicate and it will be updated in next version of the book.

  • @makeislameasy4206
    @makeislameasy4206 9 месяцев назад

    Can please give us any tips how to become pro in problem solving?

    • @SohilRathi
      @SohilRathi  9 месяцев назад +1

      Just keep practicing and you will slowly build the intuition to solve complex problems. You can use the Mastering AMC8 and Mastering AMC 10/12 books and related videos to learn all the concepts you need.

  • @jaywankhede3426
    @jaywankhede3426 4 года назад +6

    Great video good job

    • @SohilRathi
      @SohilRathi  4 года назад +2

      Thanks! Glad you enjoyed it!

  • @tomkim3544
    @tomkim3544 3 года назад

    Just wanting some more clarification, why does "choosing" correlate to combination?

    • @SohilRathi
      @SohilRathi  2 года назад +1

      because if you choose 2 pencils out of 10 for example it's just the final subset of pencils that matter

  • @mikeymonwy330
    @mikeymonwy330 4 года назад +2

    For Example 10, I don't get how you solved it. Can you please explain?

    • @SohilRathi
      @SohilRathi  4 года назад +1

      You find the number of numbers that are multiples of 2, 3, 5 but that overcounting the multiples of 2 * 3, 3 * 5, and 2 * 5. But then, the multiple of 2, 3, and 5 are being counted 3 times in the beginning, subtracted 3 times, so know we are counting it 0 times but we must count it 1 time so we add the number of multiples of 2, 3, 5 back.

  • @nannanwu4145
    @nannanwu4145 Месяц назад

    19:50 saving my lesson

  • @FamilyKonala
    @FamilyKonala 29 дней назад

    And also in math class 4, in the first problem, how did you know that there were 36 choices

    • @SohilRathi
      @SohilRathi  29 дней назад

      There are 6 choices for each dice, so the total number of choices is 6 x 6 = 36

  • @YuanMax-b6y
    @YuanMax-b6y 9 месяцев назад

    Hi for the homework question number 4 I didn’t really get no two family bring the same combination of dishes

    • @SohilRathi
      @SohilRathi  9 месяцев назад +1

      If the dish types were A, B, C, D, E etc, and if one family is bringing A, B, E, then no other family can bring ABE, but they can bring ABC, ABD, BCD, BCE, BDE. Hope it clarifies.

    • @YuanMax-b6y
      @YuanMax-b6y 9 месяцев назад +1

      ohhhh ty i ust finished my amc 8 today@@SohilRathi

  • @danielkim4151
    @danielkim4151 4 года назад +2

    Is it possible to still sign up for your online lesson or is it too late? Btw you are a great teacher!

    • @SohilRathi
      @SohilRathi  4 года назад

      Yes, you can still sign up at omegalearn.org/amc8-advanced however 3 classes are already over so you can watch the recording of those.

    • @sooji_thesnowBIGGESTfan
      @sooji_thesnowBIGGESTfan 2 года назад

      Hey daniel how you doin'

  • @anirudhvenkatesan2230
    @anirudhvenkatesan2230 4 года назад +5

    You are really awesome

  • @smaransure2234
    @smaransure2234 11 месяцев назад +1

    thx

  • @rockwithsarat8221
    @rockwithsarat8221 3 года назад +1

    is it possible to still sign up for your online sessions or is it too late?

    • @SohilRathi
      @SohilRathi  3 года назад

      There are no live classes right now, however you are welcome to sign up for future ones.

    • @abidhasan5205
      @abidhasan5205 3 года назад

      @@SohilRathi ​ but how can we join the future classes?

    • @Luckyspageturners
      @Luckyspageturners 9 месяцев назад

      @SohilRathi can I join now as well or is it too late 😢

  • @sillysillychess
    @sillysillychess 9 месяцев назад

    you should've added chapters so i could have found the questions easier!

  • @rhyneman
    @rhyneman Год назад

    Hello, this is a great channel! One question though, (even though I'm two years late hehe) for example 2, why do we use combination? If each team played the others twice, shouldn't each team have played 14 games so therefore a total of 112 conference games?

    • @SohilRathi
      @SohilRathi  Год назад

      In your method, each game is counted twice. The first teams plays and the 2nd team plays the same game. You are overcounting by a factor of 2

  • @yujianhuang8263
    @yujianhuang8263 5 месяцев назад

    do you go to aops

  • @erinshop
    @erinshop Год назад

    Hey can you explain 18:23 because I am in six grade I don’t really understand😢.

    • @SohilRathi
      @SohilRathi  Год назад +1

      Basically we need to find out how many pairs of teams are there, which is "8 choose 2" (which is 28). Then each team plays each other twice: 28 x 2 = 56.
      Each team also plays 4 games against non-conference opponents, which gives 8 x 4 = 32. So the total number of games are 56 + 32 = 88.

  • @hoeman23
    @hoeman23 9 месяцев назад

    41:50 88-16 is equal to 72

    • @SohilRathi
      @SohilRathi  9 месяцев назад

      We are doing 83 - 16

  • @belindazhumusic
    @belindazhumusic 2 года назад

    Just wondering, is this a recording?

    • @mainaccforbobby
      @mainaccforbobby 2 года назад +1

      Hi, I am not the owner, but he is a teacher for the amc8 zoom class and while he was teaching it to his student, he kindly recorded it for people like us :)

  • @FamilyKonala
    @FamilyKonala Месяц назад

    Wait in 4:26 how did the 2 numbers cancel out??????

    • @SohilRathi
      @SohilRathi  Месяц назад

      24/6 = 4, so you get a 4 in the denominator. Then 8/4 = 2, so you get a 2 in the numerator.

    • @FamilyKonala
      @FamilyKonala 29 дней назад

      Ok thank you!

  • @erinshop
    @erinshop Год назад

    Hi can you explain 26:16 pls I am a bit confused.

    • @SohilRathi
      @SohilRathi  Год назад +3

      There are 4 blue edges, 4 red edges, 4 orange edges which are parallel. Out of the 4 blue edges, any combination of 2 will be a pair of parallel edges.
      So how many pairs of blue parallel edges: "4 choose 2".
      Similarly "4 choose 2" pairs of red parallel edges,
      and "4 choose 2" pairs of orange parallel edges.
      You add them up to get the total number of pairs of parallel edges.

    • @erinshop
      @erinshop Год назад +1

      Thank you very much for replying and explaining. I understand now. ❤

  • @AdiLovesJesus4eva
    @AdiLovesJesus4eva 7 месяцев назад

    4:20 Please I don't get why the 8, 6 and 24 cancel each other

    • @SohilRathi
      @SohilRathi  7 месяцев назад +2

      8 x 6 = 48 divide that by 24, we get 2.

    • @AdiLovesJesus4eva
      @AdiLovesJesus4eva 7 месяцев назад +1

      @@SohilRathi Thanks, I've understood it now.

  • @arjunkhandelwal9174
    @arjunkhandelwal9174 4 года назад

    In the first example/introduction problem for casework at around 15:30 , you solved the case for if there were 0 5 dollar bills. But shouldn't we just ignore that because the questions ask a combination of 5 $ *and* 2$ bills. Ik that in this question it did not affect your final answer because the case didn't work, but in a question that needed a total of let say 18 dollars wouldn't it be wrong to consider a case with 0 5$ bills?
    Thanks for reading

    • @SohilRathi
      @SohilRathi  4 года назад +1

      A combination of $5 and $2 bills doesn't mean you have to include at least 1 $5 bill and at least 1 $2 bill. The problem would have specified that if that were the case.

    • @arjunkhandelwal9174
      @arjunkhandelwal9174 4 года назад

      @@SohilRathi Ok thanks

  • @saiakhilchilaka2726
    @saiakhilchilaka2726 4 года назад

    Just wondering, did you take the AMC 8? If so, what did you get?

    • @SohilRathi
      @SohilRathi  4 года назад +2

      I have taken the AMC 8 for the past 3 years and gotten honor roll when I was in 4th grade and distinguished honor in 5th and 6th grade.

    • @belindazhumusic
      @belindazhumusic 2 года назад

      @@SohilRathi Wow!

    • @shradhars9820
      @shradhars9820 7 месяцев назад

      @@SohilRathiI only took it for the first time this year and got 19/25? Is that enough to qualify for amc 10?

    • @SohilRathi
      @SohilRathi  7 месяцев назад

      @@shradhars9820 That's a pretty good score for first time. Anyone can take the AMC 10 contest and unrelated to AMC 8. So there is no qualification. You should learn AMC 10 material from the Mastering AMC 10/12 book and take the contest in November.

  • @aoiisa2149
    @aoiisa2149 5 месяцев назад

    Wait a minute is the kid the teacher or not

  • @anirudhvenkatesan2230
    @anirudhvenkatesan2230 4 года назад +1

    Explain the bottle question

    • @SohilRathi
      @SohilRathi  4 года назад

      For the bottle problem, since the 2 T's and 1 O must remain together, just treat them as 1 group. Now you have 4 objects to order: B, the group, L, E so there are 4! = 24 ways to arrange them. Now, we also must arrange the elements in the group. This can be done in 3!/2! ways by the word rearrangement formula in class 1 because there are 3 letters (T, T, O) and 2 T's so we must divide by 2!. This is equal to 3 * 2!/2! = 3. So we then, our answer is just 24 * 3 = 72 because there are 24 ways to arrange the objects and 3 ways to arrange the letters inside the group.

    • @imfrommars7362
      @imfrommars7362 Год назад

      @@SohilRathisir, why are you dividing by2 factorial? I don’t get it. Please respond ASAP. Thank you

  • @hynoph5558
    @hynoph5558 Год назад

    46:55

  • @anirudhvenkatesan2230
    @anirudhvenkatesan2230 4 года назад +1

    What grade are you in

    • @SohilRathi
      @SohilRathi  4 года назад +5

      I am currently going to 7th grade

    • @anirudhvenkatesan2230
      @anirudhvenkatesan2230 4 года назад +2

      You are so good! Which state do you live in. I am going to 7th grade too. How and where do you learn all these topics? Thanks so much!

    • @anirudhvenkatesan2230
      @anirudhvenkatesan2230 4 года назад +1

      @@poonamchauhan1318 I am 12 and live in New Jersey in the US.

    • @arthursparks-topic860
      @arthursparks-topic860 Год назад

      @@anirudhvenkatesan2230 I know where you live

    • @SamTheTurtle19
      @SamTheTurtle19 3 месяца назад

      AMC is australian math comp so he is in aus

  • @aoiisa2149
    @aoiisa2149 5 месяцев назад

    I am a third grader why should I know?

    • @SamTheTurtle19
      @SamTheTurtle19 3 месяца назад

      you will need to know these things pretty soon so better get ready

  • @redhotdippingsauce600
    @redhotdippingsauce600 4 года назад +1

    Dude, how is he still at 481 subs

  • @hudson744
    @hudson744 2 года назад

    hoiiiiii yaaaaaaaaa

  • @chyaln158
    @chyaln158 2 года назад

    56:50

  • @eden409
    @eden409 9 месяцев назад

    33:25