Question

At what percentage simple interest per annum a certain sum will double in 10 years?

• A. 7 %
• B. 8 %
• C. 9 %
• D. 10 %

Answer 1

Answer:

D. 10 %

Time = 10 years

Let the sum be Rs. X and rate of interest be r%

⇒ Amount = 2x

⇒ SI = 2x – x = x

As we know,

$SI=\frac{(P\times{r}\times{t})}{100}$

$⇒X=\frac{(X\times{r}\times{10})}{100}$

$⇒r=\frac{100}{10}$

∴ r = 10%