Question

Find the rate at simple interest, at which a sum becomes four times of itself in 15 years.

Answer 1

Let the sum be x and rate be r%

then, (x*r*15)/100 = 3x

=> r = 20%

[Important to note here is that simple interest will be 3x not 4x, because 3x+x = 4x]

Answer 2

Answer:

20%

Step-by-step explanation:

Let sum = x Then, S.I. = 3x

Rate = ( 100 × S.I / P×T)

=

$\frac{100 \times 3x}{x \times 15}$

= 20%.