The unit's place digit in the value of 2^17 is ______. A. 2 B. 3 C. 6 D. 9

GATE 2020 · General Aptitude · Unit Digit · medium

Answer: The unit digit of 2^17 is 2.

1. Identify the unit-digit cycle for powers of 2: 2^1=2, 2^2=4, 2^3=8, 2^4=16(6), 2^5=32(2) — cycle restarts.
2. Compute 17 mod 4: 17 = 4*4 + 1, so 17 mod 4 = 1. Position 1 in the cycle {2,4,8,6} corresponds to unit digit 2.