Posted by **Shay** on Monday, August 25, 2008 at 4:49pm.

seven people meet and shake hands with eachother- how many handshakes occur?

(second question)

using inductive reasoning, write a formula for the number of handshakes if the number of people is n

- Math -
**Damon**, Monday, August 25, 2008 at 6:57pm
combinations of n objects taken r at a time

C(n,r) = n!/[r!(n-r!)]

C(7,2) = 7!/[2!(5!)]

=7*3

=21

ok, reasoning

first person shakes with 6

second person with 5

third with 4

.

.

.

6th with 1

so

6+5+4+3+2+1 = 21 sure enough

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