2026 · Q30
What is the digit in the unit place of the number 1^1 x 3^3 x 5^5 x 7^7 x 9^9?
Elementary MathematicsNumber System
- A1
- B3
- C5
- D7
Explanation
The unit digits are 1, 7, 5, 3 and 9 respectively. Since 7×5=35 ends in 5, and 5 times any odd number ends in 5, the whole product ends in 5, option C. The factor 5^5 is decisive: 5 times any odd number always ends in 5, swamping the other unit digits.