Page 82 - Maths Class 05

Addition of Unlike Fractions

We must first change unlike fractions into like fractions.

1 1
Example : Let us add and .
2 4
1 1
1 1
Solution : + = ? 2 4
2 4

1
Step 1 : Find the equivalent fraction of with denominator 4.
2
1 1 × 2 2
= =
2 2 × 2 4

Step 2 : Add the like fractions.
3
2 1 2 + 1 3 4
+ = =
4 4 4 4
3 6
Example : Mary is preparing for her final exam. She studied hours on Friday,
2 4
2
hours on Saturday and hours on Sunday. How many hours she studied
3
over the weekend ?

3 6 2
Solution : + +
2 4 3

To add unlike fractions, we first change them to like fractions.

LCM of 2, 4 and 3 = 12

3 3 × 6 18 6 6 × 3 18 2 2 × 4 8
= = ; = = ; = =
2 2 × 6 12 4 4 × 3 12 3 3 × 4 12

Now, add the like fractions and express their sum in the simplest form.

18 + 18 + 8 44
= = hours
12 12

44 ÷ 4 11 11 11
= = ( HCF of 44 and 11 is 4). Hence, = 3 hours
12 ÷ 4 3 3 3
\
Addition of Mixed Numbers

There are two methods to add the mixed fractions.

3 3
Example : Add 2 and 1 .
5 10

Mathematics-5 82