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How many times can you shake hands with three people in the math wide-angle second-year teaching plan?
Three people shake hands.

If you shake hands, you can shake them twice.

However, without me, you must have two people at the same time.

So it was repeated 1 time.

Then there is

3×2÷2=3 times

The combination method is

C (3,2) = 3× 2 ÷ 2 = 3 times