Aptitude - Odd Man Out and Series - Discussion
Discussion Forum : Odd Man Out and Series - Pick Wrong No. (Q.No. 5)
Directions to Solve
Find out the wrong number in the given sequence of numbers.
5.
1, 2, 6, 15, 31, 56, 91
Answer: Option
Explanation:
1, 1 + 12 = 2, 2 + 22 = 6, 6 + 32 = 15, 15 + 42 = 31, 31 + 52 = 56, 56 + 62 = 92
Last number of given series must be 92 not 91.
Discussion:
22 comments Page 3 of 3.
Utkarsh Kumar said:
7 years ago
2 is also a prime number. So 31 cannot be the answer even if we consider this question in terms of prime numbers.
This question is solved on the basis of perfect squares. Subtract each adjacent number and you will get a perfect square, except:
91-56 = 35.
35 is not a perfect square, so we make it 36 by adding 1 to 91. Thus the final series will be as follows:
1, 2, 6, 15, 31, 56, 92
where subtracting any two adjacent numbers will give a perfect square.
I hope this helps.
This question is solved on the basis of perfect squares. Subtract each adjacent number and you will get a perfect square, except:
91-56 = 35.
35 is not a perfect square, so we make it 36 by adding 1 to 91. Thus the final series will be as follows:
1, 2, 6, 15, 31, 56, 92
where subtracting any two adjacent numbers will give a perfect square.
I hope this helps.
(9)
Rajeswari Yarra said:
2 years ago
Easy to Understand. Thanks everyone for explaining the answer.
(1)
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