Question

Find the compound interest at the rate of 5% for three years on that principal which in three years at the rate of 5% per annum gives Rs. 12000 as simple interest.

Answer 1

Given, 

Simple interest = Rs.12000 

Rate = 5% per annum 

Time = 3 years 

So,

= simple interest \(=\frac{P \times R \times \times T}{100}\)

\(=\frac{ P \times 5 \times 3}{100}\)  = 12000

\(={P}=\frac{12000\times100}{15}\) = Rs. 80000

We get , 

Principal = Rs.80000 

Rate = 5% per annum 

Time = 3 years 

Compound interest \({P}[({1}+\frac{R}{100})^T-{1}]\)

\(={80000}[({1}+\frac{5}{100})^3-{1}]\)

\(={80000}[(\frac{21}{20})^3-{1}]\)

\(={80000}\times\frac{1261}{8000}\) = Rs. 12610