A sum of money at simple interest doubles in 8 years. It will become six times in:

Correct option is C

Given:
The sum of money at simple interest doubles in 8 years.

Formula Used:-

A = P(1+RT)
A is the total amount after time T
P is the principal amount (initial sum of money),
R is the rate of interest per year 
T is the time in years.

Solution:-

Let,

P as the principal amount
R as the annual interest rate

If the money doubles in 8 years, then

​$$\text P + \text P \times \text R \times 8 = \text 2P$$

​$$\text {8PR = P}$$

​​$$\text R = \frac{1}{8} = 12.5\%$$

For time (T) it takes for the money to become 6 times the initial amount:

​$$\text {P + P }\times 0.125 \times \text T = \text {6P}$$

​​$$\text {0.125T = 5}$$

$$\text T=40$$​​​

Therefore, it will take 40 years for the money to become 6 times its initial amount at the same simple interest rate.​