Question Details

Which of the following numbers will replace the question marks (?) in the given series?
2, ?, ?, 17, 26, 37, 50, 65, 82

Options

A

3, 4

B

5, 10

C

2, 5

D

3, 5

Show Answer

Correct Answer :

Option B

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:

82-65=17

65-50=15

50-37=13

37-26=11

26-17=9

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):
2+3=5

Second missing number (3rd term):
5+5=10

We can verify our result by checking the next term (4th term):
10+7=17
This matches the 4th term in the given series.

Alternatively, each term in the series can be represented as n2+1 for n=1,2,3,4,...:

1st term: 12+1=2

2nd term: 22+1=5

3rd term: 32+1=10

4th term: 42+1=17

Therefore, the missing numbers are 5 and 10.

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