1. A borrowed some money at 3% p.a. for the 1st year, at the rate of 6% p.a. for the next 3 years, and at the rate of 9% p.a. for the period beyond 6 years. If he pays a total interest of 22800 at the end of 8 years, how much money did he borrow?
Solution:
Let the borrowed money or principal be x.
S.I = PTR/100
22800 = (x*1*3)/100 + (x*3*6)/100 + (x*4*9)/100
22800*100 = 3x + 18x + 36x
2280000 = 57x
x = 40000.
2. At what rate percent per annum will a sum of money double in 10 years?
Solution:
Here S.I = P since the amount will be doubled in 10 years.
S.I = PTR/100
R = P*100/PT
R = 100/10
R = 10 %
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