Adding & Subtracting Fractions Teacher Notes: Use this presentation to teach the steps for adding and subtracting fractions with unlike denominators.

We need a common denominator to add

these fractions.

We need a common denominator to add

these fractions.

Use Prime factorization to find the Least Common Denominator (LCD)/ Least Common Multiple (LCM)

2 7

2*1*7*1=14

14 Is the Least Common Denominator (LCD)/Least Common Multiple (LCM)

x 2

x 2

X 7

x 7 7

6

7 + 6 = 13

13

We need a common denominator to add

these fractions.

5, 10, 15, 20, 25, 30, 35, 40, 45

7, 14, 21, 28, 35, 42, 49, 56, 63

x 7

x 7

X 5

x 5 15

7

15 + 7 = 22

22

Try These

A

F

EB

C

D

Answers On Next Slide

• Each click on the next slide reveals an answer.

• Check your papers.

• If you discover an incorrect answer, be able to explain your mistake.

Try These

A

F

EB

C

D1727

1920

109

4128

2621

1312

To change a mixed number into an improper fraction get MAD…Multiply – Add – Put over Denominator

4 ½

4 x 2 = 8

8 + 1 = 992

To change an improper fraction into a mixed number divide the numerator by the denominator; whatever is left over is the new numerator…keep the same denominator.

For Example: 11

411 divided 4 equals 2; there is 3 left over. 2

34

Change the following into Improper Fractions.

1. 3 ½

2. 5 5/8

3. 12 1/3

4. 15 ¾

Change the following into Mixed Numbers.

1. 40/13

2. 100/9

3. 4/3

4. 9/2

Change the following into Improper Fractions.

1. 3 ½ = 7/2

2. 5 5/8 = 45/8

3. 12 1/3 = 37/3

4. 15 ¾ = 63/4

Change the following into Mixed Numbers.

1. 40/13 = 3 1/13

2. 100/9 = 11 1/9

3. 4/3 = 1 1/3

4. 9/2 = 4 ½

5

6

2

3

=

=

=

=

6

6

5

6

4

6

To subtract fractions you must have a

common denominator!

Find the least common

multiple for 3 and 6. (In

this case, 6) Then multiply!

1

6This is your

answer!

6th Grade HomePage

1. ½ 2. 3 ¾

- ¼ - 1 ½

3. 4 1/5

- 1 1/2

1. ½ 2. 3 ¾

- ¼ - 1 ½

¼ 2 ¼

3. 4 1/5

- 1 1/2

2 7/10