Fraction Addition

Try some

• 4/5 + 3/5

•

•

•

8

7

8

5+

12

43

12

55 +

Apples and Oranges

• The things you add have to be the same size

12

51

12

17

12

8

12

93

2

4

3

=

=+

=+

Common Denominator

Common Denominator

• A number all original denominators divide into evenly

• 12 is a common denominator because 3 and 4 both divide 12 evenly.

3

2

4

3

Least Common Denominator

• To find the least common denominator– Write the times table list for each

denominator– The smallest number that is in all rows is

the least common denominator

Least Common Denominator

• To find the least common denominator

– Write the times table list for each denominator

– The smallest number that is in all rows is the least common denominator

48,40,32,24,16,88

7

48,44,40,36,32,28,24,20,16,12,8,44

3

48,42,36,30,24,18,12,66

5

+

Try One

• Find the common denominator for these fractions

• A) 2/3 + 3/5

• B) ¾ + 7/12

• C) 2/5 + 3/8 + 7/10

Addition

• Find a common denominator

• Multiply numerator and denominator by the same number

• Add• Simplify

7

35

1

+

Addition

• Find a common denominator

• Multiply numerator and denominator by the same number

• Add• Simplify

3485

16

+

Addition

• Find a common denominator

• Multiply numerator and denominator by the same number

• Add• Simplify

2435

3612

+

Try one

• 1

835

3638

+