Transcript Dividing Fractions

WARM UP 8/28
Change these mixed numbers to
improper fractions.
Lesson Check Up
Multiply or Divide the Fractions Below
Lesson Objective: To solve math problems involving
division of fractions.
Today, we will use…
• visual fraction models
• division equations
Dividing Fractions
• What does 4 ÷ 2 mean in words? Justify your
reasoning by using a model or a drawing.
÷
how many groups of
2 are in 4?
There are 2 groups of 2 in 4, therefore
4÷ 2 = 2
Example 1
• What does 3/4 ÷ 2/3 mean in words?
(How many groups of 2/3 are in 3/4)?
Example 1
3/4 ÷ 2/3
• When dividing fractions…
Model the first fraction.
Model the second fraction.
÷
Example 1
3/4 ÷ 2/3
• Next, divide both models into the same number of
pieces… In this case it would be 12 pieces.
The # I have!
The # I want!
÷
9 = 1 1
8
8
Example 1
3/4 ÷ 2/3
• Next, find out how many groups of 2 /3 are in 3/ 4.
The # I have!
The # I want!
÷
9 = 1 1
8
8
There is 1 whole group of 8 and one
more left out of another group of 8
Example 2
Mrs. Watkins is cutting trim for her windows. She
has 1/2 yard of trim and she needs to cut her trim
into pieces that are 1/3 yard pieces. How many
pieces of trim can she cut?
1/2 ÷ 1/3
Model the first fraction.
Model the second fraction.
1/2
1/3
÷
Example 2
1/2 ÷ 1/3
• Next, divide both models into the same number of
6 pieces.
pieces… In this case it would be ___
1/2
1/3
÷
3 = 1 1
2
2
Example 2
1/2 ÷ 1/3
• Next, find out how many groups of 1 /3 are in 1/ 2.
The # I have!
The # I want!
÷
3 = 1 1
2
2
She can cut 1 whole piece and one
piece that is only half as long as
she needs.
Example 3
Mr. Shannon is making a cake for Labor Day. He
needs 1 2/3 cups of flour
but his measuring cup only measures ¾ of a cup.
How many ¾ cup portions of flour will he need to
put into the recipe?
2÷ 3
13 4
÷
Model the first fraction or
mixed number.
Model the second
fraction.
Example 3
2÷ 3
13 4
• Next, divide both models into the same number of
12 pieces.
pieces… In this case it would be ___
÷
Example 3
2÷ 3
13 4
÷
20 = 2 2
9
9
Example 3
2÷ 3
13 4
Find out how many
groups of 3/4 (9 units)
are in 1 2/3 (20 units)
÷
Mr. Shannon will need 2 whole
portions out of his measuring
cup plus 2/9’s more.
20 = 2
2
9
9
Guided Practice
SOLVE by using the S.O.A.R. method or
by making area models.
1. 1/2 ÷ 1/4
2.
1/2 ÷ 2/3
3. 2/3 ÷ 1 /2
4. 2/3 ÷ 1/4