Question

In how many years will a sum of money double itself with the rate of $10\%$ per annum simple interest?

Answer 1

Let taken time is $t$ yrs.

Also let the principle is $x$.

According to the problem after $t$ yrs the sum of money will be $2x$.

Now after $t$ yrs the sum of money will be

$x+\frac{x\times t\times 10}{100}$.

According to the problem,

$x+\frac{x\times t\times 10}{100}=2x$

or, $\frac{x\times t\times 10}{100}=x$

or, $t=10$.

So time required is $10$ years.