Select the pair of numbers that should replace the two question marks (?), in order, in the following series.
3, 11, 27, 51, ?, 123, ?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 83, 171
Look at the difference between each pair of terms. The differences are the multiples of 8 in order:
\(11-3=8\), \(27-11=16\), \(51-27=24\)
Next difference 32: \(51+32=83\)
Next difference 40: \(83+40=123\), which matches the given term
Next difference 48: \(123+48=171\)
So the missing numbers are 83 and 171.