Question

At what rate of simple interest per annum will a sum double itself in 8 years?

• A. $25\%$
• B. $6.25\%$
• C. $12.5\%$
• D. $50\%$

Answer 1

The correct option is C

$12.5\%$

Let the sum invested be P, and the rate of interest be R.

Given in 8 years, $Amount=2P$

$\Rightarrow P+SI=2P$

$\Rightarrow SI=P$

$\Rightarrow \frac{P\times T\times R}{100}=P$

$\Rightarrow T\times R=100$

$\Rightarrow R=\frac{100}{T}=\frac{100}{8}=12.5\%$