Find out the wrong number in the given sequence.
36, 54, 18, 27, 9, 18.5, 4.5
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 18.5
The terms go up and down in turn, so the rule is found from the first few terms: multiply by 1.5, then divide by 3, again and again.
\(36\times1.5=54\)
\(54\div3=18\)
\(18\times1.5=27\)
\(27\div3=9\)
\(9\times1.5=13.5\), but the series has 18.5
\(13.5\div3=4.5\), which matches the last term
The last term 4.5 fits only if the term before it is 13.5, so 18.5 is the wrong number.