Question

A sum of money at simple interest doubles itself in 4 years.in what time period will it amount to 4 times of principle

Answer 1

sorry for bad handwriting

Answer 2

The money will be four times in 12 years.

Given data :

In four years principal becomes twice.

Let,the principal amount = x

Rate = r

Now, principal+ interest = 2×x = 2x

So, interest = principal+ interest - interest = 2x-x = x

So, principal = interest

Now,

Interest = (principal × rate × time)/100

x = (x × r × 4)/100

x = rx/25

r/25 = 1

r = 25

So,the rate is 25%

Now,in the second case principal + interest = 4×x = 4x

So, interest = 4x-x = 3x

Let the time = t

Now,

Interest = (principal × time × rate)/100

3x = (x × t × 25)/100

3x = tx/4

tx/4 = 3x

t = 3x× 4/x

t = 12 (answer)