Question

Ashley, Jonathan, Sarah, Carlos, and Tanya all made the finals of the National Math Fair Competition last year. Before the final round began each one had to shake hands with all the others. How many handshakes were there? I am not really sure but the answer will be 25 or not? Thank you

Answer 1

For grade 4 let me explain it this way:

Each of the 5 people can shake hands with any of the other 4,
so that is 5x4 or 20 handshakes.

But that includes all pairs of doubles,
like Carlos vs Tanya and Tanya vs Carlos are included in the 20, but they should only count once.
So we will cut our 20 in half to get 10 handshakes.

Answer 2

25