CA Foundation · Quantitative Aptitude · Sequence and Series
The 3rd term of a GP is 12 and the 6th term is 96. What is the 9th term of this GP?
The 9th term is 768. Since the ratio of the 6th to the 3rd term is 8, the common ratio cubed is 8, so r is 2. Multiplying the 6th term 96 by r cubed, which is 8, gives 768.
- A768Correct
- B384
- C192
- D1536
Explanation
Dividing the 6th term by the 3rd gives r^3 = 96/12 = 8, so r = 2. The 9th term is the 6th term times r^3, which is 96 × 8 = 768. Choosing 384 comes from multiplying 96 by r^2 = 4 instead of r^3.
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