CA Foundation · Quantitative Aptitude · Sequence and Series
The sum to infinity of a GP is 12 and its first term is 3. What is the second term of the GP?
The second term is 9/4. From S = a/(1 − r), 12 = 3/(1 − r), so the common ratio r is 3/4. The second term equals the first term times the ratio, which is 3 × 3/4 = 9/4. The value 3/4 is the ratio itself.
- A3/4
- B9/4Correct
- C4
- D9
Explanation
Sum to infinity = a/(1 − r), so 12 = 3/(1 − r), giving 1 − r = 1/4 and r = 3/4. The second term is ar = 3 × 3/4 = 9/4. The value 3/4 is only the common ratio, not the second term.
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