A sum of money at compound interest doubles in 15 years. In how many years will it become 128 times? MCQ with Answer and Explanation

A sum of money at compound interest doubles in 15 years. In how many years will it become 128 times?

A. 90 years

B. 75 years

C. 120 years

D. 105 years

Answer: Option D

128 = 2⁷, so 15 × 7 = 105 years.

This question belongs to: Maths Compound Interest

No comments yet. Be the first to start the discussion!

Question #1 Report Error

At compound interest, if a sum becomes 8 times in 3 years, what is the rate of interest?

A. 50%

B. 100%

C. 150%

D. 200%

Correct Answer: Option B

Explanation:
(1+r)³ = 8 ⇒ 1+r = 2 ⇒ r = 100%.

This question belongs to: Maths Compound Interest

Question #2 Report Error

The compound interest on a sum for 2 years at 12% is Rs. 636. The sum is:

A. Rs. 2600

B. Rs. 2000

C. Rs. 2400

D. Rs. 2500

Correct Answer: Option D

Explanation:
CI = P[(1.12)² − 1] = P × 0.2544 = 636 ⇒ P = 636/0.2544 = 2500.

This question belongs to: Maths Compound Interest

Question #3 Report Error

At what rate percent compound interest will Rs. 10000 amount to Rs. 12100 in 2 years?

A. 15%

B. 8%

C. 10%

D. 12%

Correct Answer: Option C

Explanation:
10000(1+r)² = 12100 ⇒ (1+r)² = 1.21 ⇒ r = 10%.

This question belongs to: Maths Compound Interest