Examples of Simple Interest

Example 1:
Find simple interest on Rs. 3000 at 7% rate of interest for one year.
Solution:
Let Principal = 3000, Rate of interest = 7%, n = 1
Simple interest  =  \,\,\,\,\left( {{\text{Principal}}} \right)\left( {{\text{Rate}}} \right)\left(  n \right) = \,\,\,\,\left( {3000} \right)\,\,7\%  = \,\,\,\,3000 \times \,\frac{7}{{100}} =  \,\,\,\,210
Example 2:
Find simple interest on Rs. 10,000 at the rate of 5% for 5 years. Also find the amount for 5 years.
Solution:
Let Principal = 10,000 Rs., Rate = 5%, Time  = n = 5
Amount of simple interest for 5 years is

\begin{gathered} Interest\; = \,\,\,\,\left( {{\text{Principal}}} \right)\left(  {{\text{Interest}}} \right)\left( {{\text{Time}}} \right) = \,\,\,\,\left(  {10,000} \right)\left( {5\% } \right)\left( 5 \right) \\ Interest\;\; = \,\,\,\,\left( {10,000} \right)\left( {\frac{5}{{100}}}  \right)\left( 5 \right)\,\,\,\,\, = 2,500 \\ \end{gathered}


Hence the amount after 5 years {\text{  =  Principal}} + {\text{Interest}} =  10,000 + 2,500 = 12,500

Example 3:
Find simple interest on Rs. 156,00 for 1\frac{1}{2} years at the rate of 5% per annum. Also find total amount.
Solution:
Let Principal = 15,600, Rate = 5%  =  \frac{5}{{100}}  = 0.5, Time = 1\frac{1}{2}years   = \left( {1 + \frac{1}{2}} \right)\,\,{\text{years}}   = \frac{3}{2}\,{\text{years}}
Simple interest for 5 years  = \,\,\,\,\left( {{\text{Principal}}}  \right)\left( {{\text{Interest}}} \right)\left( {{\text{Time}}} \right) =  \,\,\,\,\left( {15,600} \right)\left( {\frac{5}{{100}}} \right)\left(  {\frac{3}{2}} \right) = \,\,\,\,1,170
Amount {\text{ =   Principal}} + {\text{Interest}} = {\text{ }}15,600 + 1,170 =  \,\,\,\,16,770

Example 4:
Find simple interest on Rs. 8,000 for 40 days, at 10% per annum.
Solution:
Let Principal = 8,000 Rs., Rate = 10% per annum, Time = 40 days  = \frac{{40\,{\text{years}}}}{{365}}   = \frac{8}{{73}}\,\,{\text{years}}
Simple interest  =  \,\,\,\,\left( {{\text{Principal}}} \right)\left( {{\text{Rate}}} \right)\left(  n \right) = \,\,\,\,\left( {8,000} \right)\left( {\frac{{10}}{{100}}}  \right)\left( {\frac{8}{{73}}} \right) = \frac{{6,400}}{{73}}

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