A sum of money at compound interest becomes 8 times in 3 years. In how many years will it become 512 times? MCQ with Answer and Explanation

A sum of money at compound interest becomes 8 times in 3 years. In how many years will it become 512 times?
A. 9 years
B. 6 years
C. 12 years
D. 7 years
Answer: Option A
Solution (By JKSSB Mock Tests)
512 = 8³, so 3 × 3 = 9 years.

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Practice More Compound Interest Questions

Question #1
What is the compound interest on Rs. 10000 for 1 year at 12% per annum, compounded half-yearly?
A. Rs. 1250
B. Rs. 1300
C. Rs. 1236
D. Rs. 1200

Correct Answer: Option C


Explanation:
Half-yearly rate = 12/2 = 6%. Time = 2 half-years. Amount = 10000 * (1 + 6/100)^2 = 10000 * 1.1236 = Rs. 11236. Compound Interest = 11236 - 10000 = Rs. 1236.

This question belongs to: Maths Compound Interest
Question #2
What is the compound interest on Rs. 40000 for 1 year at 20% per annum, compounded half-yearly?
A. Rs. 8400
B. Rs. 8800
C. Rs. 8600
D. Rs. 8000

Correct Answer: Option A


Explanation:
Half-yearly rate = 20/2 = 10%. Time = 2 half-years. Amount = 40000 * (1 + 10/100)^2 = 40000 * 1.21 = Rs. 48400. Compound Interest = 48400 - 40000 = Rs. 8400.

This question belongs to: Maths Compound Interest
Question #3
The compound interest on a certain sum of money for 2 years at 5% per annum is Rs. 328. What would be the simple interest on the same sum at the same rate for the same time?
A. Rs. 326
B. Rs. 310
C. Rs. 320
D. Rs. 324

Correct Answer: Option C


Explanation:
Effective rate of compound interest for 2 years at 5% = 5 + 5 + (55)/100 = 10.25%. Simple interest rate = 5 * 2 = 10%. Given 10.25% of sum = 328 => 1% of sum = 32. Simple Interest = 10% of sum = 10 * 32 = Rs. 320.

This question belongs to: Maths Compound Interest