Question

in what time will a sum of money lent at 8 1 by 3% simple interest become 4 times of itself .

Answer 1

The amount will take 100 years to become 4 times of it at 3% Simple Interest

1) Let the lent amount be P.

2) Rate of Interest = 3%.

3) Desired Amount = 4P.

i.e. Simple Interest = 4P-P = 3P

4) Formula for Simple Interest is :

SI = PRT/100

3P = P*3*T/100

This equates to T = 100 years.

Answer 2

Let the amount lent be rs x.

at the rate of 8 1/3%

Amount expected is 4 times the x = 4x rs

Simple interest = a - p = 4x - x = 3x rs.

but

simple interest = PRT / 100

3x = X x 25/3 x T / 100

3x = X/3 x T /4

3x x 4 = X/3 x T

12X X 3 / X =T

T = 36 years.