Find the number which does not fit into the series given below.
3, 7, 19, 53, 163, 487
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 53
The terms grow about three times each step. The rule is multiply by 3, then subtract 2; check each term:
\(3\times3-2=7\)
\(7\times3-2=19\)
\(19\times3-2=55\), but the series has 53
\(55\times3-2=163\), which matches the next term
\(163\times3-2=487\), the last term
The term after it fits only if the fourth term is 55; with 53 it would be \(53\times3-2=157\). So 53 does not fit the series.