Choose the number that will come next in the following series.
80, 71, 75, 66, 70, 61, ?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 65
The series goes down and up in turn, so look at the steps: they are −9 and +4 alternately.
\(80-9=71\), \(71+4=75\)
\(75-9=66\), \(66+4=70\)
\(70-9=61\)
The next step is +4: \(61+4=65\)
So the next number is 65.