# Question #8b177

Oct 2, 2017

24

#### Explanation:

Let the sum (P) be x. It becomes double means 2x in 8 (T) years.

It means Interest (I) = 2x - x = x. we have to fine the rate of interest

(R) from here.

We know, I = PRT/100

$\Rightarrow x = \frac{x . R . 8}{100}$

$\Rightarrow R = \frac{100}{8}$

Again, Sum (P) = x, sum + interest = 4x. Interest (I) = 4x - x = 3x

Rate of interest (R) = 100/8 and we have to find no. of years (T)

We know I = PRT/100

$\Rightarrow 3 x = \frac{x . \frac{100}{8.} T}{100}$

$\Rightarrow \frac{100}{8.} T = 300$

$\Rightarrow T = 300 \times \frac{8}{100} = 24$