2020 · Q6
If the sum of the digits of a number 10^n − 1, where n is a natural number, is equal to 3798, then what is the value of n?
Elementary MathematicsNumber System
- A421
- B422
- C423
- D424
Explanation
10ⁿ − 1 is the n-digit number 999…9, whose digits are all 9. Its digit sum is therefore 9n. Setting 9n = 3798 gives n = 422.