A. 7 years

B. 10 years

**C. 15 years**

D. 20 years

Explanation:

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P(1 + R/100)^{5} = 2P => (1 + R/100)^{5} = 2

Let P(1 + R/100)^{n} = 8P

=> (1 + R/100)^{n} = 8 = 23 = {(1 + R/100)^{5}}^{3}

=> (1 + R/100)^{n} = (1 + R/100)^{15} => n = 15 Required time = 15 years.

### Related Mcqs:

- A sum of money placed at compound interest doubles itself in 5 years in how many years it would to 8 times of itself at the same rate of interest?
A. 7 years

B. 10 years

**C. 15 years**

D. 20 years - A sum of money place at compound interest doubles itself in 4 years. In how many years will it amount to eight times itself?
A. 16

B. 8

**C. 12**

D. 20 - A man invests a certain sum of money at 6% per annum simple interest and another sum at 7% per annum simple interest. His income from interest after 2 years was Rs. 354. One-forth of the first sum is equal to one-fifth of the second sum. The total sum invested was :
A. Rs.3100

**B. Rs.2700**

C. Rs.2200

D. Rs.1800 - The sum of money at compound interest amounts to thrice itself in 3 years. In how many years will it be 9 times itself?
A. 18

B. 12

C. 9

**D. 6** - Simple interest on a certain sum of money for 3 years at 8% per annum is half the compound interest on Rs. 4000 for 2 years at 10% per annum. The sum placed on simple interest is:_______?
A. Rs. 1550

B. Rs. 1650

**C. Rs. 1750**

D. Rs. 2000 - A sum amount to Rs.1344 in two years at simple interest. What will be the compound interest on the same sum at the same rate of interest for the same period?
A. Rs.150

B. Rs.140

C. Rs.130

**D. Data insufficient for the answer** - Eight years ago, Zahid’s age was 4/3 times that of Shahid. Eight years hence, Zahid’s age will be 6/5 times that of Shahid. What is the present age of Zahid?
A. 30 years

**B. 40 years**

C. 32 years

D. 48 years

E. None of these - The simple interest on Rs.12000 at a certain rate of interest in five years is Rs.7200. Find the compound interest on the same amount for five years at the same rate of interest.
A. Rs.3502.80

B. Rs.3052.40

C. Rs.3054.8

**D. Rs.3052.80**

E. None of these - A sum of money trebles itself in 15 years, 6 months. In how many years would it double itself ?
A. 6 years 3 months

**B. 7 years 9 months**

C. 8 years 3 months

D. 9 years 6 months - A sum of Rs. 725 is lent in the beginning of a year at a certain rate of interest. After 8 months, a sum of Rs. 362.50 more is lent but at the rate twice the former. At the end of the year, Rs. 33.50 is earned as interest from both the loans. What was the original rate of interest?
**A. 3.46%**

B. 4.5%

C. 5%

D. 6%

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