Add Fractions with Unlike Denominators

Use least common denominator to find the sum of fractions with unlike denominators.

For example: Let's find the sum of:

2 7

and

1 4

Notice that 28 is the common denominator.

First of all, rewrite both the fractions having common denominator 28.

Multiply the numerator and denominator of

2 7

by 4 to find an equivalent fraction.

2 7

×

4 4

=

8 28

Multiply the numerator and denominator of

1 4

by 7 to find an equivalent fraction.

1 4

×

7 7

=

7 28

Now add fractions. Add numerators and keep denominators the same.

2 7

+

1 4

=

8 28

+

7 28

=

15 28

is written in simplest form.

 

So, the required sum is

15 28

.