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Introduction

As in previous chapter, discussed about what is fraction and what are its types. Now in this chapter, here is topic operations on fractions. All basic operations can be done on fractions i.e addition, subtraction, multiplication and division of fractions. In this chapter, addition, subtraction, multiplication and division of fractions will be discussed.

Addition of fractions

1. Addition of like fractions

In addition of fractions of like fractions, only numerators are added and keep the value of denominator as it is.

Example

Example 1: Add 5 8 and 6 8
As the denominator is 8 and add numerator of both fractions only
= 5 8 + 6 8
= 5 + 6 8 = 11 8


Example 2: Add 1 4 , 2 4 and 6 4
Here, as denominator is 4 for all fractions, so add numerators of all fractions only.
= 1 4 + 2 4 + 6 4
= 1 + 2 + 6 4 = 9 4

2. Addition of unlike fractions

To add unlike fractions, convert unlike fractions into like fractions by taking LCM of their denominators.

Example

Example 1: Add 3 4 and 5 6
Step 1: Take LCM of denominators of fractions. 3 4 and 5 6 .
Step 2: Multiply both fractions by numbers to make their denominators same equal to LCM 12.
3 4 × 3 3 = 9 12
5 6 × 2 2 = 10 12
Step 3: Add the like fractions 9 12 and 10 12 .
= 9 12 + 10 12
= 9 + 10 12 = 19 12
= 9 + 10 12 = 19 12
3 4 + 5 6 = 19 12


Example 1: Add 2 3 , 4 6 and 1 4
Step 1: Take LCM of denominators of fractions 2 3 , 4 6 and 1 4
Step 2: Multiply all fractions by numbers to make their denominators same equal to LCM 12.
2 3 × 4 4 = 8 12
4 6 × 2 2 = 8 12
1 4 × 3 3 = 3 12
Step 3: Add the like fractions 8 12 , 8 12 and 3 12
= 8 12 + 8 12 + 3 12
= 8 + 8 + 3 12 = 19 12
2 3 + 4 6 + 1 4 = 19 12

Subtraction of fractions

1. Subtraction of like fractions

In subtraction of like fractions, only numerators are subtracted and keep the value of denominator as it is.

Example

Example 1: Subtract 8 9 from 10 9
As these are like fractions and denominator is 9 for both fractions.
So, subtract numerator of both fractions only.
= 10 9 8 9
= 10 – 8 9 = 2 9


Example 2: Subtract 11 12 from 15 12
Here, the two fractions are like fractions and their denominator is 12.
So, subtract numerators of both fractions only.
= 15 12 11 12
= 15 – 11 12 = 4 12 = 1 3

2. Subtraction of unlike fractions

To subtract the unlike fractions, convert unlike fractions into like fractions by taking LCM of their denominators.

Example

Subtract 6 4 from 8 3
Step 1: Take LCM of denominators of fractions.
LCM of 4 and 3 is 12
Step 2: Convert unlike fractions into like fractions by multiplying a number which makes denominator equal to LCM 12.
8 3 × 4 4 = 32 12
6 4 × 3 3 = 18 12
Step 3: Subtract 18 12 from 32 12
= 32 12 18 12
= 32 – 18 12 = 14 12 = 7 6
8 3 6 4 = 14 12

Multiplication of fractions

1. Multiplication of fraction with whole number

To multiply a fraction with whole number, multiply only numerator by the given whole number and keep the denominator same. Then reduce it to its the lowest term.

Example

Example 1: 7 5 × 2
Here, 7 5 is a fraction and 2 is a whole number.
2 is written as 2 1
= 7 5 × 2 1
= 7 × 2 5 × 1 = 14 5


Example 2: 6 5 × 4
= 6 5 × 4 1
= 6 × 4 4 × 1 = 24 5

2. Multiply a fraction by another fraction

To multiply a fraction by another fraction, multiply their corresponding numerators and denominators. Then reduce the obtained fraction into its the lowest form.

Example

Example 1: Multiply fraction 7 5 by 3 4
Here, multiply numerators 7 and 3. Also, multiply their denominators 5 and 4.
7 5 × 3 4
= 7 × 3 5 × 4 = 21 20


Example 2: Multiply fractions 2 5 , 4 6 and 3 2
2 5 × 4 6 × 3 2
multiply numerators 2, 4 and 3 and also multiply denominators 5, 6 and 2.
= 2 × 4 × 3 5 × 6 × 2 = 24 60
Now 24 60 should be reduced to its the lowest term by dividing with the common factor 12.
24 60 = 2 5

Division of fractions

To divide a fraction with another fraction, first the division is changed into multiplication by changing the division sign into multiplication and taking reciprocal of the second fraction.
Let’s learn it by following examples.

Example

Example 1: Divide 2 3 by 5 7
= 2 3 ÷ 5 7
= 2 3 × 7 5
= 2 × 7 3 × 5 = 14 15


Example 2: Divide fraction 4 5 by whole number 6
= 4 5 ÷ 6 1
= 4 5 × 1 6
= 4 × 1 5 × 6 = 4 30
4 30 . should be reduced into its the lowest term by dividing with common factor 2
= 2 15


Example 3: Divide 5 by 6 7
= 5 ÷ 6 7
= 5 × 7 1 × 6
= 35 6