"Shake hands with 3 people": Can we use combinations?

Question

Can we use combinations?

Answer

To put it bluntly, no. Try not to think too much about who shakes hands with who, because we're not asked about that - the problem encourages generalization by saying "if each person shakes hands with exactly 3 other people...", so take that at face value: each person gets 3 handshakes.

Link

http://gre.magoosh.com/questions/858