Question

A sum of money doubles itself in 8 Years .What is the rate of interest?

Answer 1

Answer:12.5%

Step-by-step explanation:

Let the principal be x.

SI=P*R*T/100

x=x*R*8/100

R=100/8%

R=12.5%

Answer 2

$\huge\bf\underline{Answer :-}$

$\large{\underline{\boxed{\sf Rate \: = \: 12.5 \%}}}$

$\huge\bf\underline{Solution :-}$

Let the rate be 'r'

Let the principal pe 'x'

.°. The amount is '2x'

Hence, S.I => (2x - x) = x

Given,

Time = 8 years

According to question,

$\sf S.I = \dfrac {P \times R \times T}{100}$

$\sf\longrightarrow x = \dfrac {x \times r \times 8}{100}$

$\sf\longrightarrow x = \dfrac {2x \times r}{25}$

$\sf\longrightarrow r = \dfrac {25 \times x}{2x}$

$\huge\sf\therefore r = 12.5 \%$

Hence, At the rate of 12.5% p.a, a sum of money will double itself in 8 years.