## 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%