What is the unit digit in the expansion of 7^105?

A1

B3

C7

D9

Explanation

Cyclicity of 7 is 4 (7, 9, 3, 1). Divide exponent 105 by 4: remainder is 1. Unit digit is 7^1 = 7.

Exam Relevance

Topic: Number System
Subtopic: Unit Digit

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