virtus
There are 7 people at a party and they shake each other's hand once. How many hand shakes are there?



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estudier
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A person can only shake the hand of 6 others.....

virtus
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i don't think that is right

smr_kml
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Thank you

virtus
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for...

smr_kml
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you know for what!

mukushla
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C(2,7)=21

virtus
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thats correct @mukushla
but where does the 2 come from?

virtus
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is it because person A shakes hands with person B
And then person B shakes hands with person A

estudier
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One can shake 6 so there are 7 by 6 but this counts a single handshake twice.

higgs
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^they can't shake hands twice

virtus
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oh i see so why is it 7C2?

virtus
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like i get how you say its like 6+5+4+3+2+1 =21 which is the same ans as 7C2

virtus
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@higgs the answer is 21 according to my solution book

estudier
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Forget the handshakes, how many ways to choose 2 from 7 without regard to order?

virtus
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why choose 2 from 7

estudier
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2 people (ie 2 hands)

virtus
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ohhhh i see , wow i guess thats a nice way to think about it