Question Details

What number should replace question Mark(?1) in the series given below.

55, 47, 74, 10, 135, 81, 262?

Options

A

774

B

-250

C

343

D

-343

Show Answer

Correct Answer :

Option B

-250

Solution :

The correct option is -250.

To find the missing number in the series, let us analyze the pattern of differences between consecutive terms:
55, 47, 74, 10, 135, -81 (printed as 81 in the question due to a sign typo), 262, ?

The sequence progresses by alternately subtracting and adding the cubes of consecutive integers starting from 2:

1 st term = 55

2 nd term = 55 - 2 3 = 55 - 8 = 47

3 rd term = 47 + 3 3 = 47 + 27 = 74

4 th term = 74 - 4 3 = 74 - 64 = 10

5 th term = 10 + 5 3 = 10 + 125 = 135

6 th term = 135 - 6 3 = 135 - 216 = - 81
(Note: The question contains a minor typo where -81 is written as 81.)

7 th term = - 81 + 7 3 = - 81 + 343 = 262

Following this established logical mathematical pattern, the next term is obtained by subtracting the cube of 8:

8 th term = 262 - 8 3 = 262 - 512 = - 250

Therefore, the number that should replace the question mark is -250.

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