## virtus 3 years ago There are 7 people at a party and they shake each other's hand once. How many hand shakes are there?

1. estudier

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

2. virtus

i don't think that is right

3. smr_kml

Thank you

4. virtus

for...

5. smr_kml

you know for what!

6. mukushla

C(2,7)=21

7. virtus

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

8. virtus

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

9. estudier

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

10. higgs

^they can't shake hands twice

11. virtus

oh i see so why is it 7C2?

12. virtus

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

13. virtus

@higgs the answer is 21 according to my solution book

14. estudier

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

15. virtus

why choose 2 from 7

16. estudier

2 people (ie 2 hands)

17. virtus

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