AMC / AIME · Pigeonhole Principle · Easy

Pigeonhole Principle: What is the minimum number of people needed to guarantee that two share a birth month?

Forced collisions.

Try the problem

What is the minimum number of people needed to **guarantee** that two share a birth month?

Hint and answer

Concept to use

Basic form.

Hint

1212 months → 12+112+1.

Answer

13

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