Answer: 45 handshakes.
Step-by-step explanation:
We have 10 kids.
Let's count.
Kid 1, can meet other 9 kids, so here we have 9 handshakes.
Kid 2, he can meet other 9 kids, but he already handshaked kid 1, so here we only count 8 handshakes.
Kid 3, he can meet other 9 kids, but we already counted the handshake with kid 1 and kid 2, so from here we only count 7 handshakes.
You can see the pattern, the total number of handshakes will be:
H = 9 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1 = 45
