Question

A bank gives 10% simple interest on deposits by senior citizens. Draw a line graph to illustrate the relation between the sum deposited and the simple interest earned.
Find from the graph:
(i) The annual interest obtainable for a investment of Rs 250
(ii) The investment one has to make in order to get an annual simple interest of Rs 70

Answer 1

$$\begin{gathered} \mathrm{Using}SI=\frac{P\times R\times T}{100} \\ \mathrm{Where}\mathrm{SI}=\mathrm{simple}\mathrm{interest} \\ \mathrm{P}=\mathrm{principal} \\ \mathrm{R}=\mathrm{rate}\mathrm{of}\mathrm{interest} \\ \mathrm{T}=\mathrm{time} \end{gathered}$$

We have,

P	500	1000	1500	2000
SI	50	100	150	200

(i) Given sum deposited i.e P = 250 , R = 10%, Time = 1 year
using formula we have,

$$\begin{gathered} SI=\frac{250\times 10\times 1}{100} \\ SI=25\mathrm{Rs} \end{gathered}$$

Hence, the annual interest for an investment of 250 rs is 25 rs.

(ii) Given annual simple interest = 70 rs , R = 10%, T=1 year
using formula we have,

$$\begin{gathered} 70=\frac{P\times 10\times 1}{100} \\ 700=P \\ \mathrm{Hence},\mathrm{he}\mathrm{has}\mathrm{to}\mathrm{invest}700\mathrm{rs}\mathrm{in}\mathrm{order}\mathrm{to}\mathrm{get}\mathrm{an}\mathrm{annual}\mathrm{simple}\mathrm{interest}\mathrm{of}70\mathrm{rs} \end{gathered}$$