Question Details

What number would replace question mark (?) in the series given below?

3, 8, 17, 32, 57, ?, 177

Options

A

100

B

89

C

95

D

106

Show Answer

Correct Answer :

Option A

100

Solution :

The correct option is: 100.

To find the missing number in the given series, let us analyze the differences between consecutive terms:


First level of differences:
8-3=5
17-8=9
32-17=15
57-32=25

Now, let us find the differences between these first-level differences (the second level of differences):


Second level of differences:
9-5=4
15-9=6
25-15=10

If we look closely at the sequence of second differences (4, 6, 10, ...), we can observe a pattern in the differences between them (the third level of differences):


Third level of differences:
6-4=2
10-6=4

The differences in the third level are doubling (2, 4, ...). Following this pattern, the next third-level differences should be 8 and then 16.

Using this logic, we can work backwards to find the missing terms:


The next second-level difference: 10+8=18
The subsequent second-level difference: 18+16=34

Now, we find the next first-level differences by adding these values to the previous first-level differences:


The next first-level difference: 25+18=43
The subsequent first-level difference: 43+34=77

Finally, we calculate the missing term (?) in our original sequence:


The missing number replacing the question mark (?): 57+43=100

We can verify this by checking if it leads to the final number in the series (177) using the subsequent difference of 77:


Verification: 100+77=177

Since the calculations match the given sequence, the number that replaces the question mark is indeed 100.

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