A sum of money invested at compound interest doubles itself in 9 years. In how many years will it become 8 times of itself? MCQ with Answer and Explanation

A sum of money invested at compound interest doubles itself in 9 years. In how many years will it become 8 times of itself?

A. 36 years

B. 45 years

C. 18 years

D. 27 years

Answer: Option D

The sum doubles (2^1) in 9 years. It will become 8 (2^3) times in 3 * 9 = 27 years.

This question belongs to: Maths Compound Interest

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Question #1 Report Error

The difference between compound interest and simple interest on Rs. 2000 for 3 years at 5% per annum is:

A. Rs. 16.00

B. Rs. 15.50

C. Rs. 16.50

D. Rs. 15.25

Correct Answer: Option D

Explanation:
CI − SI = P × (R/100)² × (3 + R/100) = 2000 × 0.0025 × 3.05 = 2000 × 0.007625 = Rs. 15.25.

This question belongs to: Maths Compound Interest

Question #2 Report Error

What is the principal if the amount after 2 years at 10% compound interest is Rs. 12100?

A. Rs. 12000

B. Rs. 11000

C. Rs. 10000

D. Rs. 13000

Correct Answer: Option C

Explanation:
P = 12100 / (1.1)² = 12100 / 1.21 = 10000.

This question belongs to: Maths Compound Interest

Question #3 Report Error

A sum of money at compound interest doubles in 12 years. In how many years will it become 64 times?

A. 48 years

B. 84 years

C. 72 years

D. 60 years

Correct Answer: Option C

Explanation:
64 = 2⁶, so 12 × 6 = 72 years.

This question belongs to: Maths Compound Interest