Question

At simple interest a sum becomes 6/5 of itself in 4 years. What is the rate of interest

Answer 1

Let : P = Principal amount , R = Rate % , T = Time then :
P +$\frac{P * R * T}{100}$ = $\frac{6}{5}P$
$\frac{100P + PR4}{100}$ =$\frac{6}{5}P$
500P + 20PR = 600P
P(500 + 20R) = 600P
500 + 20R = 600
20R = 100
R = 5 % Ans.

Answer 2

Rate=Interest×100/principal ×Time
=6×100/4×5
=600/20
=30%