CA Foundation · Quantitative Aptitude · Sequence and Series
Which term of the GP 3, 6, 12, 24, ... equals 768?
768 is the 9th term. The nth term is 3 times 2 to the power n minus 1. Setting this equal to 768 gives 2 to the power n minus 1 equal to 256, which is 2 to the power 8, so n is 9.
- A9thCorrect
- B8th
- C10th
- D7th
Explanation
Here a = 3 and r = 2, so the nth term is 3 × 2^(n−1) = 768. Then 2^(n−1) = 256 = 2^8, so n − 1 = 8 and n = 9. The answer 8th comes from taking n equal to the exponent rather than adding 1.
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.
More Sequence and Series questions
- Which of the following is the general term (nth term) of the sequence 2, 5, 10, 17, 26, ...?
- Four arithmetic means are inserted between 7 and 32. What is the third of these means?
- If x, y, z are in AP, which expression must be the arithmetic mean of x and z?
- If the sum of the first n terms of an AP is 3n² + 2n, what is the common difference of the AP?
- The sequence 2, 6, 12, 20, 30, ... has its nth term equal to n(n+1). Which term of this sequence equals 240?
- The sum of three numbers in AP is 27 and the sum of their squares is 293. What is the largest of the three numbers?