Question

Find the principal if the compound interest at the rate of 5% per annum compounded annually for 3 years is Rs 1261.

Answer 1

Dear student,

$$\begin{gathered} LetthePrincipalbe\text{'}P\text{'} \\ weknow, \\ A=P{\left(1+\frac{R}{100}\right)}^t \\ \Rightarrow A=P{\left(1+\frac{5}{100}\right)}^3 \\ \Rightarrow A=P{\left(1+\frac{1}{20}\right)}^3 \\ \Rightarrow A=P{\left(\frac{21}{20}\right)}^3 \\ \Rightarrow A=P\left(\frac{9261}{8000}\right) \\ Also,CI=A-P \\ \Rightarrow 1261=\frac{9261}{8000}P-P \\ \Rightarrow 1261=\frac{9261P-8000P}{8000} \\ \Rightarrow 1261=\frac{1261P}{8000} \\ \Rightarrow \frac{\cancel{1261}\times 8000}{\cancel{1261}}=P \\ \Rightarrow P=Rs8000 \end{gathered}$$

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