Everyone at a party shook hands. There were 210 handshakes in all. How people attended the party?

Question

anonymous · Answer

Have you tried anything so far?

anonymous · Answer

Oh, nothing? :(

OK, let's start with looking at some small cases and try and find a general pattern.

If two people go, the first person shakes hands with the second, and that is it.
 3 people:

1-> 2, 3
2-> 3

And we are done.

anonymous · Answer

You could try looking at slightly larger groups, but you may notice a pattern soon?

dumbcow · Answer

is what iNewton said make sense?
the pattern should lead you to combinations
there are 210 possible handshakes among n people
handshake takes 2 people so there are 210 pairs among n people
nC2 = 210
combinations equation
n!/(n-2)!*2! = 210
solve for n