SIMPLE INTEREST

:. Rate = 8% and Time = 8 years.
Ex. 9. A man borrowed Rs 24000 from two money lenders. For one loan, he paid 15% per
annum and for the other 18% per annum. At the end of one year, he paid Rs 4050. How much
did he borrow at each rate ?
Sol. Let the sum at 15% be Rs x and that at 18% be Rs (24000 - x).
.. {(X x 15 x 1)/100 + {[(2400 – x) X 18 X 1]/100} = 4050
or 15 x + 432000 - 18x = 405000 or x = 9000.
:. Money borrowed at 15% = Rs 9000 .
Money borrowed at 18% = Rs 15000.
Ex. 10. What annual instalment wiU discharge a debt of Rs 1092 due in 3 years at 12% simple
interest?
Sol. Let each instalment be Rs. x . then,
{ [x + (X x 12 x 2)/100] + [ X + (X + 12 x 2)/100] + x} =1092
or 28x/25 + 31x/25 +x=1092 or (28x+ 31x+25x) = (1092x25)
or X= {(1092 x 25)/84} = 325
:. Each instalment = Rs. 325
Ex.11 A sum of money invested for a certain number of years at 8% p.a. simple interest
grows to Rs.180. The same sum of money invested for the same number of years at 4% p.a.
simple interest grows to Rs.120 only. For how many years was the sum invested?
Solution:
From the information provided we know that,
Principal + 8% p.a. interest on principal for n years = 180 …….. (1)
Principal + 4% p.a. interest on principal for n years = 120 ……… (2)
Subtracting equation (2) from equation (1), we get