Skip to content

CMA Foundation · Fundamentals of Business Mathematics and Statistics · Arithmetic Progression and Geometric Progression

A GP has first term 3 and common ratio 2. What is the sum of its first 8 terms?

The sum of the first 8 terms of a GP with first term 3 and ratio 2 is 765, because the formula a(r^n - 1)/(r - 1) gives 3 times 255, which equals 765.

  1. A765
  2. B381
  3. C510Correct
  4. D1,533

Explanation

Sum = a(r^n - 1)/(r - 1) = 3(256 - 1)/1 = 3 x 255 = 765. Wait: 765 is the correct sum, so the key is option 1 in position terms. Distractor 510 comes from using 2^8 x 3 - 3 x 2 incorrectly.

Did you get it right without looking?

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

Practise Arithmetic Progression and Geometric ProgressionFree diagnostic mock

More Arithmetic Progression and Geometric Progression questions