Transcript Multiplying With Fractions

Tuesday 9/2 Quick Review

Review Video
Improper and Mixed Fractions
Multiplying
With
Fractions
I can multiply fractions.
Just Follow These Easy
Steps!



Multiply the numerators
Multiply the
denominators
Simplify
Example 1
5 x 3
15
=
32
8
4
There are no common factors for
15 and 32, so this fraction cannot
be simplified.
Example 2
3
4
2
6
1
x
=
=
9
36
6
This fraction can be reduced. Divide the
numerator and denominator by the GCF,
which is 6.
Multiplying by a Whole
Number
If you want to multiply a fraction by a
whole number, turn your whole number into
a fraction by placing a 1 as the
denominator.
4
20
80
x
= 5 = 16
5
1
Another Example
15 x 1
5
15
=
=
1
6
6
2
15 and 6 have a GCF of 3.
2
2 5
4
1
Five halves is improper, so we
divide the bottom into the top.
2
1
2
Simplifying Factors



Before you multiply, you can make the problem
simpler.
You can find the GCF of any numerator and
denominator.
Find a factor that equally divides the top number
and bottom number, divide, and rewrite the
problem.
Example 1
5 x 81
16 2
7
5
14
In the second fraction, 8
and 16 have a GCF of 8.
8 ÷ 8 = 1 and 16 ÷ 8 = 2
Now, multiply with the
simpler numbers. 5 x 1 = 5
and 7 x 2 = 14.
Example 2
12
5
x
12 6
3
Now, multiply:
5
18
The top of the first fraction and
the bottom of the second fraction
have a common factor. The GCF
of 2 and 12 is 2.
2 ÷ 2 = 1, and 12 ÷ 2 = 6.
Homework Time!
Textbook
Page 107
1-10
Sponge Wednesday
September 3
1)
3) List the steps
on how you
would multiply
a fraction by a
fraction.
Multiplying Mixed
Numbers
You can NEVER MULTIPLY OR DIVIDE
mixed numbers!!!!!
Steps:
1) Make each mixed number an improper
fraction.
2) Multiply numerators
3) Multiply denominators
4) SIMPLIFY
Mixed Number
Examples….

Examples on your
own….
Page 115 1-9
(ODD’s ONLY)
Dividing a Whole Number by a
Fraction
What is 3 ÷ ¼ ?
Use your prior knowledge and the illustration above to figure it
out. Think, “If I start with 3, how many groups that look like ¼
will I have?”
Dividing a Whole Number by a
Fraction
1
2
3
4
5
6
9
10
7
8
11
12
If you start with 3, you will have 12 groups of 1/4 .
So, 3 ÷ ¼ = 12.
Can you see how you could manipulate the fractions to get an answer of 12?
Dividing a Whole Number by a
Fraction
What is 5 ÷ 1/3?
If you start with 5, you will have 15 groups of 1/3 .
So, 5 ÷ 1/3 = 15.
Can you see how you could manipulate the fractions to get an answer of 15?
Steps….
1)
2)
3)
4)
5)
Make the whole number a
fraction by putting a 1 in the
denominator
Keep the first fraction the same
Change the division sign to
multiplication
Flip (take the reciprocal) of the
second fraction
Now you use Multiplication
Steps 
Examples:

Homework
Page 139
2-12 (EVEN’s ONLY)
Sponge Thursday
September 4
Homework Check
Vocabulary:
Reciprocal

When you flip the second fraction, you are
writing that fraction’s reciprocal.
3
5
5
3
To Divide Fractions by
Fractions:
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Rewrite the first fraction.
Change the division sign to a multiplication
sign.
Flip the second fraction upside down.
Multiply.
Example 1
1
3
÷
1
2
Rewrite:
1 x 2
2
=
1
3
3
Example 2
4
4
÷
5
9
Rewrite:
14
9
9
4
x
=
=1
4 1
5
5
5
Review Example 3
12 ÷ 3
5
1
Rewrite:
4 12 x 5 = 20 = 20
1
31
1
Review Example 4
1
6
÷
2
1
Rewrite:
1
1 x 1
=
6
2
12
Re-cap of today’s lesson
Dividing Fractions Re-cap
Homework Page 153
18-21; 23-26
Friday Sponge
September 5
Explain the steps you
need to complete to
divide fractions by
fractions.
Divide Mixed Numbers
Check Homework
Change any mixed numbers into improper
fractions.
Change any whole numbers into improper
fractions by putting 1 under the whole number.
KEEP – CHANGE - FLIP.
Multiply numerators and denominators
Simplify
Example 1
1
1
9
10
9
1 10
3 9
÷
6
2
3
÷
20
3
x
3 1
20 2
=
1
6
More Practice…
Example 2:
Example 3:
6 ÷ 3½
1 ½ ÷ 3 ¾
On your own….
Textbook Page 159
(1-3)
Quiz –Take out a sheet of paper
and write your name on it 
Homework:
Review videos on web
blog from this week’s
lessons 