Find a wrong number in a series: 7, 28, 63, 124, 215, 342, 511
Find a wrong number in a series:
7, 28, 63, 124, 215, 342, 511.
A. 7
B. 28
C. 124
D. 215
E. 342
Sol:
Clearly the correct sequence is : 23−1,33−1,43−1,53−1,63−1,73−1,83−1.
∴28 is wrong and should be replaced with33−1 i.e. 26. Hence, the answer is (b).