Example.1
What is the compound interest on Rs.10240 at
25% p.a. for one and a half year compounded semi-annually? .
Solution
A = P
Here R = 12.5% and n = 3 .
A = 10240
A = 10240
A = 
=
Rs.14580
\ Compound interest = 14580 -
10240 = 24340. .
example.2
What is the compound interest on Rs.10000 at
40% p.a. for 9 months, interest being compounded quarterly? .
Solution
A = P
Here, P = Rs.10000, R = 10% and n = 3 .
A = 10000
= 13310
Compound interest = 13310 - 10000 = Rs.3310 .
example.3
What sum becomes Rs.10368 in 3 years at 20%
p.a compound interest compounded annually? .
Solution
A = P
Given, 10368 = P
10368 = P
&⇒ P = 
=
Rs.6000
example.4
At what
rate of simple interest a sum of money doubles itself in 12 years?
Solution
Let the
Principal be Rs.P. .
Then amount = 2P
So, simple interest = 2P - P = P
So R = 
example.5
A sum of money becomes 27 times itself in 3
years at compound interest. Find the rate of interest per annum. .
Solution
Let Principal be Rs.P. So amount = 27P .
27P = P
&⇒ =27
&⇒ 1 + 
= 3
&⇒ R = 200%
