What is the next number of the following sequence ? 21, 77, 165, 285, ......

A)
437
B)
426
C)
415
D)
401

Correct Answer : Option (A) - 437

Explanation :

The series follow the rule :
 
21 = 5²-4 
77 = 9²−4
165 = 13²−4
285 = 17²−4
 
5,9,13,17,21,(+4)...
In the same way next no. will be
21²−4 = 441 - 4 = 437

Recently Updated in Mental Ability Questions
Q .
In the following question :
Various terms of an alphanumerical series are given with one or more terms missing as shown by (?). 
Choose the missing terms out of the given alternatives. BMO, EOQ, HQS, ?
A)
SOV
B)
LMN
C)
KSU
D)
SOW

Correct Answer :   KSU

Explanation : The first letter moves 3 steps forward. The second and third letters move 2 steps forward.

Q .
What should come in place of the question mark (?) in the following number series? 8, 6, 9, 23, ?
A)
35
B)
49
C)
62
D)
87

Correct Answer :   87

Explanation :

Given number 8, 6, 9, 23, ?
 
The pattern of given series is :
8 x 1 - 2 = 6 6 x 2 - 3 = 9 9 x3 - 4 = 23 23 x4 - 5 = 87