Subtracting Fractions Get ready to become an expert at subtracting fractions & mixed numbers!

Subtracting Fractions

Get ready to become an expert at subtracting fractions & mixed

numbers!

Subtracting with the same denominator.

Subtracting fractions that have the same denominator is simple. You

subtract the numerators and write the difference over the common

denominator. If your answer is an improper fraction, re-write it as a

mixed number.

Example:

56

16

-

46

=23 Solve on your

own. Click for the

answer!

Subtracting fractions with different denominators.Subtracting fractions with different denominators is impossible. In order for fractions to be subtracted from one another, they must have the

same number of parts. The denominator represents the number of parts. Therefore, you must find a

common denominator.

Why?

You have a 5/6 of a pizza left. You eat 1/4 of the pizza that is remaining. How much of leftover pizza

remains now?

A common denominator is necessary so that each piece of pizza is the same size and can be added with the others. What is a common denominator

for 6 and 4?12

- =

What are the steps?

To subtract fractions:

1. Find a common denominator if there isn’t one already. 2. Convert each of your fractions into an equivalent

fraction using the common denominator. 3. Subtract the numerators.4. Write the difference as the numerator in your answer.

The denominator will be your common denominator.5. If your answer is an improper fraction, convert to a

mixed number. Simplify if necessary.

35

47

-

35

Click for the answer!

What is the least common denominator?

3547-

Click for the answer!

How do you re-write the fractions using the common denominator?

35

35

=

=x 5

x 5

x 7

x 721

20

Solve:

35

47

-

135

=

Rewrite using the least common

denominator, then solve on your own.

Click for the answer!

2135

2035

-

What is the least common denominator?

78

15

-

40

Click for the answer!

Solve:

78

15

-

2740

=

Rewrite using the least common

denominator, then solve on your own.

Click for the answer!

3540

840

-

Solve:

56

23

-

16

=

Rewrite using the least common

denominator, then solve on your own.

Click for the answer!

56

46

-

When you subtract multi-digit numbers, do you subtract

from:

Right to left? Left to right?

Right to Left!

For example: 485123

You subtract 5-3 first!-

When we subtract mixed numbers, we do the same

thing!

Right to Left!Subtract the fractions before the whole

numbers

For example: 4 ¾ 1 ¼3

You subtract ¾ - ¼ first!-

24

But Why?

We subtract the fractions before the whole numbers in order to determine if we need to

borrow from the whole number.

Example:

-23

4 14

2

-

2314

=-

8123

12

Click to move through the

problem visually.

512

Example:

-23

4 14

2Click to move through the

problem visually.

512

You already figured out that - is

23

14

512

Next, subtract the whole numbers

4 – 2 = 2

2 + = 2512

512

We subtract the fractions before the whole numbers in order to determine if we need to

borrow from the whole number.

What are the steps?

To subtract mixed numbers:

1. Find a common denominator if there isn’t one already. 2. Convert each of your fractions into an equivalent fraction

using the common denominator. 3. Subtract the numerators.

• If you cannot subtract the numerators because the first numerator is smaller than the second, you need to borrow a whole from the first whole number and add it onto the first fraction.

4. Write the difference as the numerator in your answer. The denominator will be your common denominator.

5. If your answer is an improper fraction, convert to a mixed number.

6. Simplify if necessary.7. Subtract the whole numbers.8. Combine with the fraction difference if necessary.

Solve:

45

12

4 - 2

310

=

Rewrite using the least common

denominator, then solve on your own.

Click for the answer!

810

510

-4 – 2 = 2

310

2 + = 2310

Solve:

34

13

6 - 3

512

=

Rewrite using the least common

denominator, then solve on your own.

Click for the answer!

912

412

-6 - 3 = 3

512

3 + = 3512

Solve:

310

14

7 - 1

120

=

Rewrite using the least common

denominator, then solve on your own.

Click for the answer!

620

520

-7 – 1 = 6

120

6 + = 6120

What If?

4723-

We can’t subtract 14 from 12… So now what?

What if you re-write your fractions using a common denominator, and the first fraction

is larger than the second?

21

21

=

=x 7

x 7

x 3

x 312

14

2

1

4723-

Click to see the steps you take to solve a problem like this!

You need to “borrow” a whole from the whole number part of the first mixed

number.

21

21

=

=x 7

x 7

x 3

x 3 12

14

2

1

1. Borrow 1 from the 2 in the form of a fraction.

2121

2. To make it easy on you, write the fraction as the common denominator over the common denominator.

13. Add your borrowed whole onto the fraction.

4. Now you can subtract!

+3321

=

1921

5. Simplify if necessary.

1234-

You Try!Solve on your own, then click to check your

answer.

4

4

=

=

x 2

x 2 2

3

5

2

2. Borrow 1 from the 4 in the form of a fraction. 4

43. To make it easy on you, write the fraction as the common denominator over the common denominator.

34. Add your borrowed whole onto the fraction.

5. Now you can subtract!

+64

=

34

1. Rewrite with a common denominator