Competition problem — Number theory

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Number theory Difficulty 5.3 AIME, harder Find the answer

4. Using Fermat's little theorem, find the last digit of the base 7 expansion of $3^{100}$ .

Your answer

A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.

Solution

4. 4

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Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic and difficulty added by this site.