Find the next number in the series: 1, 3, 6, 10, 15, ?
- A. 22
- B. 18
- C. 21 ✓
- D. 20
Correct answer
C. 21
Explanation
The difference between terms increases by 1 each time (2,3,4,5), so the next difference is 6, giving 15 + 6 = 21.
C. 21
The difference between terms increases by 1 each time (2,3,4,5), so the next difference is 6, giving 15 + 6 = 21.