Question

Find the wrong term in the sequence: 24, 27, 31, 33, 36, 39

& (A)24 \\\ & (B)27 \\\ & (C)31 \\\ & (D)33 \\\ & (E)39 \\\ \end{aligned}$$

Answer 1

Initially, wn second term and first term. In a similar way, we have to find the difference between third term and second term, we have to list all the given terms in the series. Now we have to find the difference between difference between fourth term and third term, difference between fifth term and fourth term and difference between fifth term and sixth term. Now we have to observe if there is any change in difference between consecutive numbers. Based on this concept, we have to solve the problem.

Complete step-by-step answer :
From the given series, it is clear that the first term is equal to 24, the second term is equal to 27, the third term is equal to 31, the fourth term is equal to 33, the fifth term is equal to 36 and sixth term is equal to 39.
Now we have to find the difference between each consecutive term.
Difference between second term and first term $=27-24=3$
Difference between third term and second term $=31-27=4$
Difference between fourth term and third term $=33-31=2$
Difference between fifth term and fourth term $=36-33=3$
Difference between sixth term and fifth term $=39-36=3$
So, it is clear that in most of the cases 3 is the common difference.
We are having the change in difference between the difference between third term and second term and difference between fourth term and third term.
So, it is clear that the number 31 may be an incorrect number in the given series.
If we place 30 instead of 31, the series can be corrected.
Hence, option C is correct.

Note : student should be careful at calculation part of this question. If a small mistake is made, then it is not possible to get a correct final answer. So, one should do the calculation part in a perfect manner. This is also important to solve this problem. Students should also have a clear view where the common difference gets violated. One should understand in which way the number can be changed to have a perfect series. This concept should be clear to any student.