Which of the following numbers will replace the question mark (?) in the given series?
17, 21, 28, 38, 51, 67, ?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1, i.e., 86.
17 + 4 = 21, 21 + 7 = 28, 28 + 10 = 38, 38 + 13 = 51, 51 + 16 = 67, 67 + 19 = 86