How many zeros does 100 factorial end in? Count the fives.

One hundred factorial, 158 digits long. The story asks how many zeros it ends in. You type your answer and check it. Then you step through the answer and the breakdown.

Why quant interviews test this

A quick test of turning 'zeros' into 'factors of five'. Expect a follow-up on 1000!. The written solution is at /brain-teasers/trailing-zeros/solution.

The Trailing Zeros of 100! guide covers how scoring works, the strategy that wins, a worked example and the mistakes most players make.

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