Question

A sum of money is doubled in 8 years at r% rate of compound interest per annum. At the same rate in how
many years it will be four times of the sum?​

Answer 1

Step-by-step explanation:

Let the sum of money that's principal be x.

Time=8 years

Amount after 8 years becomes double=2x

Therefore,

Simple interest=Amount -principal=2x−x=x

Rate per annum =

P×T

S.I×100

=

x×8

x×100

=

8

100

=

2

25

=12.5%

Then,

We get interest of 8years is 12.5%