A sum of money triples itself in 6 years at compound interest. In how many years will it become 9 times? MCQ with Answer and Explanation

A sum of money triples itself in 6 years at compound interest. In how many years will it become 9 times?

A. 9 years

B. 12 years

C. 15 years

D. 10 years

Answer: Option B

3 times in 6 years, 9 = 3² ⇒ 6 × 2 = 12 years.

This question belongs to: Maths Compound Interest

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Question #1 Report Error

A sum of money invested at compound interest doubles itself in 20 years. In how many years will it become 4 times of itself?

A. 40 years

B. 60 years

C. 50 years

D. 30 years

Correct Answer: Option A

Explanation:
The sum doubles (2^1) in 20 years. It will become 4 (2^2) times in 2 * 20 = 40 years.

This question belongs to: Maths Compound Interest

Question #2 Report Error

A sum of money at compound interest becomes 9 times in 4 years. In how many years will it become 81 times?

A. 8 years

B. 10 years

C. 7 years

D. 6 years

Correct Answer: Option A

Explanation:
81 = 9², so 4 × 2 = 8 years.

This question belongs to: Maths Compound Interest

Question #3 Report Error

The difference between simple interest and compound interest on a certain sum of money for 2 years at 7% per annum is Rs. 49. Find the sum.

A. Rs. 10000

B. Rs. 12000

C. Rs. 11000

D. Rs. 9000

Correct Answer: Option A

Explanation:
Difference for 2 years = P * (R/100)^2 => 49 = P * (7/100)^2 => 49 = P * (49 / 10000) => P = Rs. 10000.

This question belongs to: Maths Compound Interest