Complete the following series with the correct option: 3, 2, 6, 8, 18, 40, ?

The series is two interleaved sequences. Odd positions give 3, 6, 18, and even positions give 2, 8, 40. The odd-position terms are multiplied by 2, then 3, then 4, so 3 to 6 to 18 to 72. The even-position terms are multiplied by 4, then 5, which is the pattern 2 to 8 to 40. The next term is in an odd position, so it is 18 times 4, which gives 72, option C.

Why the others fail: 70 and 75 do not come from any multiplicative step in the pattern. 75 would need an addition of 35 to 40, which breaks the sequence. 71 is prime and has no clean link to 18 or 40.

Core concept: interleaved or alternating series, where you split the terms by position and test each subsequence separately. This is standard in UPPSC reasoning and it helps in Mains-style data and pattern analysis too.

Trap: aspirants look only at the successive differences of the full series, find no tidy pattern, and guess. Always test odd and even positions separately before giving up on a series.