Word Problem 9

Problem 9: If a man finds that increase in interest rate from 4-7/8 to 5-1/8 percent per annum on his investment increases his income by Rs 25. What is his invested amount?

a) 10000                   b) 12000                c) 15000              d) 20000


simple arithmetic questions and answers

This is basically problem of simple interest.

We suppose

Investment = x Rs

But it is given that  1st Simple Interest ( SI)

SI= \frac{4\frac{7}{8}}{100} \times x

\Rightarrow SI = \frac{39}{800}x

And 2nd SI;

SI2= \frac{5\frac {1}{8}}{100}x

\Rightarrow SI2 = \frac{41}{800}\times x

We take difference of both simple interests;

Difference = SI - SI2

\Rightarrow Difference =\frac{41}{800}x- \frac{39}{800}x

\Rightarrow Difference =\frac{2}{800}x

But this difference should be equal to increase in income i-e Difference = 25RS, so;

\Rightarrow 25 =\frac{2}{800}x

Keep ‘x’ on one side and shift remaining term to other side;

x= 25 \times \frac{800}{2}

x= 25 \times 400 = 10000

x= 10000 Rs

So invested amount was RS 10000