UPSC Prelims 2024·CSAT·Quantitative Aptitude·Number System

What is the unit digit in the expansion of (57242)^(9×7×5×3×1)?

Dalvoy logo
Reviewed by Dalvoy
UPSC Civil Services preparation
Last updated 23 May 2026, 3:31 pm IST
  1. A2Correct
  2. B4
  3. C6
  4. D8

Explanation

The exponent is 9 × 7 × 5 × 3 × 1 = 945. The unit digit of 57242 is 2. The unit digit cycle of powers of 2 is: 2, 4, 8, 6 (period 4). 945 mod 4 = 1. So the unit digit of 2^945 = 2. Therefore the answer is A (2).
Quantitative Aptitude: What is the unit digit in the expansion of (57242)^(9×7×5×3×1)?

Related questions

More UPSC Prelims practice from the same subject and topic.