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

Question

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. 50 years

B. 60 years

C. 30 years

D. 40 years

Answer: Option D

Solution (By JKSSB Mock Tests)

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

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Question #1

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The compound interest on Rs. 3000 at 5% per annum for 3 years is:

A. Rs. 478.00

B. Rs. 472.50

C. Rs. 475.00

D. Rs. 472.875

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Correct Answer: Option D

Explanation:
A = 3000 × (1.05)³ = 3000 × 1.157625 = 3472.875, CI = 3472.875 − 3000 = Rs. 472.875.

This question belongs to: Maths Compound Interest

Question #2

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A sum of money at compound interest becomes 3 times in 4 years. In how many years will it become 9 times?

A. 10 years

B. 12 years

C. 8 years

D. 6 years

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Correct Answer: Option C

Explanation:
3 times in 4 years, 9=3² ⇒ 4×2=8 years.

This question belongs to: Maths Compound Interest

Question #3

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The difference between CI and SI on a sum for 2 years at 10% is Rs. 150. The sum is:

A. Rs. 15000

B. Rs. 14000

C. Rs. 13000

D. Rs. 12000

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Correct Answer: Option A

Explanation:
D = P × 0.01 = 150 ⇒ P = 15000.

This question belongs to: Maths Compound Interest

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