Question

In the table below, principal, period and rate have been given. Use the formula to find the simple interest in each case.

Example	Principal (Rs)	Period (years)	Rate of interest p.c.p.a
(1)	700	6	5
(2)	1800	$7\frac{1}{2}$	9
(3)	12000	4	$5\frac{1}{2}$
(4)	15500	2	$7\frac{1}{2}$
(5)	10500	$5\frac{1}{2}$	$6\frac{1}{2}$

Answer 1

(1) Principal (P) = Rs 700
Time (N) = 6 years
Rate (R) = 5 p.c.p.a
We have $\mathrm{I}=\frac{\mathrm{P}\times \mathrm{R}\times \mathrm{N}}{100}$
$$\begin{gathered} \Rightarrow \mathrm{I}=\frac{700\times 5\times 6}{100} \\ \Rightarrow \mathrm{I}=7\times 5\times 6 \\ \mathrm{Therefore},\mathrm{I}=\mathrm{Rs}210 \end{gathered}$$

(2) Principal (P) = Rs 1800
Time (N) =$7\frac{1}{2}\mathrm{years}=\frac{15}{2}\mathrm{years}$
Rate (R) = 9 p.c.p.a
We have $\mathrm{I}=\frac{\mathrm{P}\times \mathrm{R}\times \mathrm{N}}{100}$
$$\begin{gathered} \Rightarrow \mathrm{I}=\frac{1800\times 9\times {\displaystyle \frac{15}{2}}}{100} \\ \Rightarrow \mathrm{I}=\frac{900\times 9\times 15}{100} \\ \Rightarrow \mathrm{I}=9\times 9\times 15 \\ \mathrm{Therefore},\mathrm{I}=\mathrm{Rs}1215 \end{gathered}$$

(3) Principal (P) = Rs 12000
Time (N) = 4 years
Rate (R) =$5\frac{1}{2}=\frac{11}{2}\mathrm{p}.\mathrm{c}.\mathrm{p}.\mathrm{a}$
We have $\mathrm{I}=\frac{\mathrm{P}\times \mathrm{R}\times \mathrm{N}}{100}$
$$\begin{gathered} \Rightarrow \mathrm{I}=\frac{12000\times {\displaystyle \frac{11}{2}}\times 4}{100} \\ \Rightarrow \mathrm{I}=\frac{6000\times 11\times 4}{100} \\ \Rightarrow \mathrm{I}=60\times 11\times 4 \\ \mathrm{Therefore},\mathrm{I}=\mathrm{Rs}2640 \end{gathered}$$

(4) Principal (P) = Rs 15500
Time (N) = 2 years
Rate (R) = $7\frac{1}{2}=\frac{15}{2}\mathrm{p}.\mathrm{c}.\mathrm{p}.\mathrm{a}$
We have $\mathrm{I}=\frac{\mathrm{P}\times \mathrm{R}\times \mathrm{N}}{100}$
$$\begin{gathered} \Rightarrow \mathrm{I}=\frac{15500\times {\displaystyle \frac{15}{2}}\times 2}{100} \\ \Rightarrow \mathrm{I}=\frac{15500\times 15\times 1}{100} \\ \Rightarrow \mathrm{I}=155\times 15\times 1 \\ \mathrm{Therefore},\mathrm{I}=\mathrm{Rs}2325 \end{gathered}$$

(5) Principal (P) = Rs 10500
Time (N) = $5\frac{1}{2}\mathrm{years}=\frac{11}{2}\mathrm{years}$
Rate (R) =$6\frac{1}{2}=\frac{13}{2}\mathrm{p}.\mathrm{c}.\mathrm{p}.\mathrm{a}$
We have $\mathrm{I}=\frac{\mathrm{P}\times \mathrm{R}\times \mathrm{N}}{100}$
$$\begin{gathered} \Rightarrow \mathrm{I}=\frac{10500\times {\displaystyle \frac{13}{2}}\times {\displaystyle \frac{11}{2}}}{100} \\ \Rightarrow \mathrm{I}=\frac{2625\times 13\times 11}{100} \\ \mathrm{Therefore},\mathrm{I}=\mathrm{Rs}3753.75 \end{gathered}$$