Question

If a certain sum becomes n times in t years formula

Answer 1

Let Principal = P, Rate = R% per annum, Time = T years and A = Amount due after 3 years

A=P

(1+

R100

)

3

8P=P

(1+

R100

)

3

8=

(1+

R100

)

3

2=1+R100

1=R100

R=100

A=P(1+R100)38P=P(1+R100)38=(1+R100)32=1+R1001=R100R=100



Solution 2 (using formula)

If a certain sum becomes n times in t years, then the rate of compound interest 

=

[

n

(1/t)

−1]

×100%=

[

8

(1/3)

−1]

×100%

=(2−1)×100%

=100%

=[n(1/t)−1]×100%=[8(1/3)−1]×100%=(2−1)×100%=100%