Ex.8.3 Q10 Compairing Quantities - NCERT Maths Class 7

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What rate gives \(\rm Rs \,280\) as interest on a sum of \(\rm Rs\, 56,000\) in \(2\) years?

Text Solution

What is Known?

Principal, interest and number of years. 

What is Unknown?

Rate of interest.


Rate of Interest can be calculated using the formula

Simple Interest  

\[\begin{align} & =\frac{\left[ \begin{align} & \text{Principal} \times  \text{Rate of interest} \\ &  \times  \text{Time (in years)} \\ \end{align} \right]}{100} \\ \end{align}\]


Let us assume that rate of interest to be \(\rm{R.}\)

So, Simple Interest 

\[\begin{align}{\rm{ = }}\,\frac{{{\rm{Principal}}\,{\rm{ \times Rate}}\,{\rm{ \times }}\,{\rm{Time}}}}{{{\rm{100}}}}\end{align}\]

\[\begin{align}{\rm{I}}{\rm{.E}\,}{\rm{.\,280}}\, &=\frac{{{\rm{56000}} \times {\rm{R}}\, \times {\rm{2}}}}{{{\rm{100}}}}\\{\rm{R}} &= \frac{{280 \times 100}}{{56000 \times 2}}\\ &= 0.25\%\end{align}\]

So, the rate of interest is \(0.25\%\)