Question

A sum of money becomes 8by5 of itself in 5 years at a certain rate of simple interest. Find the rate of interest.

Answer 1

Step-by-step explanation:

principal = x

amount =8/5 x

time 5 yrs

since, amt =principal +interest

8/5 x=x+ xR5

[ interst =PRT, Let rate be R ]

on solving R is 12%

hope it helps

Answer 2

Answer :-

Rate of interest is 16 %

Explanation :-

Let the principal be P

Time (T) = 5 yeaers

Amount (A) = 8/5 of P = (8/5) * P = 8P/5

Amount = Principal + Interest

⇒ 8P/5 = P + Interest

⇒ (8P/5) - P = Interest

⇒ (8P - 5P)/5 = Interest

⇒ 4P/5 = Interest

⇒ Interest = 4P/5

Let the rate of interest be 'R' %

We know that

Simple Interest = PTR/100

⇒ 4P/5 = P * 5 * R/100

⇒ 4P/5P = 5R/100

⇒ 4/5 = R/20

⇒ (4/5) * 20 = R

⇒ (4 * 20)/5 = R

⇒ 4 * 4 = R

⇒ 16 = R

⇒ R = 16

i.e Rate of interest = 16 %

∴ Rate of interest is 16 %