UPSC CSE 2025 · PYQ · Number System / Unit Digit · easy
What is the unit digit in the multiplication of 1 × 3 × 5 × 7 × 9 × . . . × 999 ?
Answer
The correct answer is C: 5. The product is of all odd numbers from 1 to 999. Since 5 is one of the factors, and the other factors include odd numbers, the product will end in 5 (any odd number multiplied by 5 gives a number ending in 5).
A.1
B.3
C.5✓ Correct
D.9
Explanation
The product is of all odd numbers from 1 to 999. Since 5 is one of the factors, and the other factors include odd numbers, the product will end in 5 (any odd number multiplied by 5 gives a number ending in 5). Therefore, the unit digit of the entire product is 5.
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