Which of the following numbers will replace the question marks (?) in the given series?
2, ?, ?, 17, 26, 37, 50, 65, 82
Correct Answer :
5, 10
Solution :
The correct option is 5, 10.
To find the numbers that replace the question marks in the series, let us analyze the pattern of differences between consecutive terms.
Given series: 2, ?, ?, 17, 26, 37, 50, 65, 82
Let us check the differences between the known consecutive terms toward the end of the series:
Notice that the differences between successive terms are consecutive odd numbers: 9, 11, 13, 15, 17.
Extending this pattern backward, the differences preceding 9 should be consecutive smaller odd numbers, which are 3, 5, and 7.
Now, let us calculate the missing numbers step-by-step using these differences:
First missing number (2nd term):
Second missing number (3rd term):
We can verify our result by checking the next term (4th term):
This matches the 4th term in the given series.
Alternatively, each term in the series can be represented as for :
1st term:
2nd term:
3rd term:
4th term:
Therefore, the missing numbers are 5 and 10.
Access expert-curated educational resources and study materials—completely free.
Create, conduct, and manage professional online assessments with Mindyard. Perfect for teachers and institutes.
Copyright © 2026 Mindyard. All Rights Reserved.