Skip to content

CA Foundation · Quantitative Aptitude · Sequence and Series

If the sum of the first n terms of an AP is 3n² + 2n, what is the common difference of the AP?

The common difference is 6. The first term is S1=5 and S2=16 gives the second term 11, so the difference is 6. Equivalently, the coefficient of n² in the sum formula equals half the common difference.

  1. A3
  2. B5
  3. C6Correct
  4. D2

Explanation

S1=5 so a=5. S2=12+4=16, so the second term is 11. Common difference = 11-5 = 6. In general the coefficient of n² is d/2, so d=6. Option 3 wrongly takes the coefficient itself as d.

Did you get it right without looking?

One question tells you little. A timed set on Sequence and Series shows your real accuracy, how long you take and where you lose marks.

Practise Sequence and SeriesFree diagnostic mock

More Sequence and Series questions