Railway Recruitment Board Mathematics — Question 1686
Question
What is the unit digit of 7^105?
- 9
- 3
- 1
- 7
Correct answer
D — 7
Explanation (English)
Unit digits of powers of 7 cycle with period 4: 7, 9, 3, 1. Divide the exponent by 4: 105 ÷ 4 leaves remainder 1, so the unit digit is the 1st in the cycle = 7.
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