Question

a sum of money becomes 8/5 of itself in 5 years at a certain rate of interest. Find the rate of interest

Answer 1

here is your answer.
P will cancel out P.
and rate of interest= 32%
please mark it as brainliest Answer.
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Answer 2

Answer:

The rate of interest is 12%.

Step-by-step explanation:

It is given that a sum of money becomes 8/5 of itself in 5 years at a certain rate of interest.

Let the sum of money be x and the rate of interest is r.

The amount is 8/5 of principal after 5 years.

$A=\frac{8}{5}x$

$I=A-P$

$I=\frac{8}{5}x-x$

$I=\frac{8x-5x}{5}x=\frac{3x}{5}$

So, the interest is $\frac{3x}{5}$.

The formula for interest is

$I=\frac{P\times r\times t}{100}$

Where, P is principal, r is rate of interest in % and t is time in years.

$\frac{3x}{5}=\frac{x\times r\times 5}{100}$

Divide both sides by x.

$\frac{3}{5}=\frac{r}{20}$

Multiply both sides by 20.

$\frac{3}{5}\times 20=r$

$12=r$

Therefore the rate of interest is 12%.