The Cassette Recorder

If there are 24 people at a beach party and each person shakes another person’s hand, how many handshakes are there?

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276 handshakes.

Each person can shake hands with 23 other people, so we have 24 × 23 possible combinations. But because it takes two people to make a handshake, we must divide this product by 2, so we get (24 × 23)/2 = 276.

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