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anonymous

  • 5 years ago

100 people are present in a party. If each of them must do a handshake with all the other people, how many handshakes should be done? Please explain how to get the answer, thanks!

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  1. anonymous
    • 5 years ago
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    you need 2 people for an hand shake and u have 100 people so i think that its C(100,2) but i am not sue of it..

  2. anonymous
    • 5 years ago
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    \[\sum_{n=1}^{99}n=\frac{1}{2}\times99\times100=4950\]

  3. anonymous
    • 5 years ago
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    Could you solve it using factorials, please?

  4. anonymous
    • 5 years ago
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    hmm i found the answer as 9900

  5. amistre64
    • 5 years ago
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    if there are 3 people: 1,2 ; 1,3 ; 2,3 .... is that right?

  6. anonymous
    • 5 years ago
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    Think about it like this: the first person has 99 people to shake hands with, the second person has 98 because they've already shaken hands with the first, the third has 97...

  7. anonymous
    • 5 years ago
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    yea but its harder to calculate this like that... so i think C(100,2) better way of solve

  8. amistre64
    • 5 years ago
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    5054 if we do that ..... add all the numbers from 1 to 100 :)

  9. anonymous
    • 5 years ago
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    No, all the numbers from 1 to 99.

  10. amistre64
    • 5 years ago
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    n(n+1) ------ :) 2

  11. amistre64
    • 5 years ago
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    ack .... 99 then lol

  12. amistre64
    • 5 years ago
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    wouldnt the last guy have noone to shake hands with?

  13. anonymous
    • 5 years ago
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    mhmh yea but there is 100 people and they and we need 2 people to shake hands so that it should be 100 x 99 /2,

  14. anonymous
    • 5 years ago
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    Yeah, the last guy has no-one to shake hands with, that's why it's sum of the first 99 integers, not the first 100.

  15. anonymous
    • 5 years ago
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    yea you right

  16. amistre64
    • 5 years ago
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    5.4321 4.321 3.21 2.1 1.0 i get 5 people with 10 shakes 5(4)/2 = 10 8.7654321 7.654321 6.54321 5.4321 4.321 3.21 2.1 1.0 8 people with 28 shakes 8(7)/2 = 28 I spose it works :) 100(99)/2 = 99*50 = 4950 yay!!

  17. anonymous
    • 5 years ago
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    Glad we agree.

  18. amistre64
    • 5 years ago
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    factorial would be: 100! 100*99 ---------- = ------- 2! (100-2)! 2

  19. anonymous
    • 5 years ago
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    its the same with C(100,2)

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