Question

A person deposited Rs.100 in a bank and gets the amount Rs.121 after two years. The rate of compound interest is​

Answer 1

${\huge{\underline{\red{Given\: :-}}}}$

Principal = ₹100

Amount = ₹121

Time = 2 years

${\huge{\underline{\red{To\: Find\: :-}}}}$

The Rate of Interest.

${\huge{\underline{\red{Formula\: :-}}}}$

${\sf{Amount\: =\: P\: \bigg(1\: +\:{\dfrac{r}{100}}\: \bigg)^n}}$

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

${\sf{121\: =\: 100\: \bigg(1\: +\:{\dfrac{r}{100}}\: \bigg)^2}}$

${\sf{\implies\: {\dfrac{121}{100}}\: =\: \bigg(1\: +\:{\dfrac{r}{100}}\: \bigg)^2}}$

${\sf{\implies\: \sqrt{1.21}\: =\: \bigg(1\: +\:{\dfrac{r}{100}}\: \bigg)}}$

${\sf{\implies\: 1.1\:=\: \bigg(1\: +\:{\dfrac{r}{100}}\: \bigg)}}$

${\sf{\implies\: 1.1\: -\: 1\: =\: {\dfrac{r}{100}}}}$

${\sf{\implies\: r\: =\: 0.1\: \times\: 100}}$

${\sf{\implies\: r\: =\: \bold{10}}}$

${\huge{\fbox{\blue{Rate\: =\: 10\%\: }}}}$