Question

A sum of money is invested at compound interest payable annually. The interest in two
successive year is Rs 225 and Rs 240. Find
(i) the rate of interest
(ii) the original sum
(iii) the interest earned in third ​

Answer 1

Answer:

Interest for Rs 225 for 1- year = Rs (240–225) = Rs 15

So rate of interest= 15/225 x 100= (20/3%) = 6⅔%

Now at 6⅔% rate of interest the accrued interest = Rs 225

So the Principal amount

= Rs(100/ 6⅔) x 225 = Rs 3375

Check : Interest for year-I

=Rs. 3375 x 20/3 x 1/100

= Rs 3375 x 20/300 = Rs 225

Compound interest for 2- years

= Rs. 3375 x (1+20/300)²

= Rs. 3375 x (320/300)²

=Rs. 3840

Compound interest for the second year =3840-(3375+225)= Rs. 240.

Answer 2

Answer:

Interest for Rs 225 for 1- year = Rs (240–225) = Rs 15

So rate of interest= 15/225 x 100= (20/3%) = 6⅔%

Now at 6⅔% rate of interest the accrued interest = Rs 225

So the Principal amount

= Rs(100/ 6⅔) x 225 = Rs 3375

×××××××××××××××××××××××××××××

Check : Interest for year-I

=Rs. 3375 x 20/3 x 1/100

= Rs 3375 x 20/300 = Rs 225

Compound interest for 2- years

= Rs. 3375 x (1+20/300)²

= Rs. 3375 x (320/300)²

=Rs. 3840

Compound interest for the second year =3840-(3375+225)= Rs. 240.