CA Foundation · Quantitative Aptitude · Sequence and Series
The 3rd term of a GP is 18 and the 6th term is 486. What is the 8th term of this GP?
The 8th term is 4374. Dividing the 6th term by the 3rd gives r cubed = 27, so r = 3. The first term is 18/9 = 2. The 8th term is then 2 multiplied by 3 to the power 7, which equals 4374.
- A4374Correct
- B1458
- C13122
- D2916
Explanation
ar^5 / ar^2 = r^3 = 486/18 = 27, so r = 3. Then a = 18/9 = 2. The 8th term = 2 × 3^7 = 2 × 2187 = 4374. Option 13122 is the 9th term (2×3^8), a one-term overshoot, and 1458 is the 7th term (2×3^6).
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
- A company's sales are ₹2,00,000 in the first year and grow by 5% every year. Using (1.05)^4 = 1.2155, what are the total sales over the firs…
- What is the value of the sum 1×2 + 2×3 + 3×4 + ... + 10×11?
- A sequence is defined by the rule t(n) = 2n² − 3n + 1. What is the sum of its 3rd and 5th terms?
- Two positive numbers a and b have AM = 10 and GM = 8. Which of the following is the value of the HM, and what is the correct relationship be…
- Which of the following sequences is neither an arithmetic progression nor a geometric progression?
- If the sum of the first n terms of an AP is 3n² + 5n, which of the following is the common difference and the 15th term respectively?