2025 · Q63
How many three-digit numbers are there that have the middle digit as the sum of the first digit and the third digit?
General Mental Ability, Quantitative Aptitude and StatisticsNumber system
- A40
- B45
- C50
- D55
Explanation
Let the digits be a (1-9), b, c (0-9) with b = a + c <= 9. For a = 1 there are 9 values of c (0-8), for a = 2 there are 8, and so on down to 1 value for a = 9. The total is 9+8+...+1 = 45.