One term is wrong in the following series. Find that wrong term – 4, 15, 64,…
2022
One term is wrong in the following series. Find that wrong term – 4, 15, 64, 5, 25, 125, 6, 36, 216
- A.
64
- B.
25
- C.
36
- D.
15
Attempted by 134 students.
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Correct answer: D
Answer: 15 is the wrong term.
Reason:
Group the sequence into triples: (4, 15, 64), (5, 25, 125), (6, 36, 216).
Each triple follows the pattern n, n^2, n^3.
For n = 4 the middle term should be 4^2 = 16, but the sequence has 15 instead. Therefore 15 is incorrect; it should be 16.
The other terms (64 = 4^3, 25 = 5^2, 125 = 5^3, 36 = 6^2, 216 = 6^3) match the pattern and are correct.