Transcript 4-3 Multiplying Fractions

1.) 4 – 2 3/8 =
43
- 2
1
8
8
3
8
5
8
2.) 5 1/9 – 2 8/9 =
45
- 2
2
1 + 9 = 10
9 9 9
8
9
2
9
3-4 Multiplying Fractions
3-5 Dividing Fractions
Multiplying Fractions
Big Rocks
1. Simplify if needed
2. Multiply numerators
3. Multiply denominators
Multiply. Write the answer in simplest form.
A. –12 ·
3
4
Write –12 as a fraction.
3
–12 ·
Simplify.
3 = – 12 · 3
4
1
4
1
Multiply numerators.
Multiply denominators.
=– 9 =–9
1
Remember!
You can write any integer as a fraction with a denominator of 1.
Additional Example 2B: Multiplying Fractions
Multiply. Write the answer in simplest form.
B. 1·
3
.
3
8
1
1 ·3 = 1
3 8
8
1
Simplify.
Multiply numerators.
Multiply denominators.
Try This: Example 2B
Multiply. Write the answer in simplest form.
B. 1·
6
.
6
9
1
1 ·6 = 1
9
6 9
1
Simplify.
Multiply numerators.
Multiply denominators.
Additional Example 3A: Multiplying Mixed Numbers
Multiply. Write the answer in simplest form.
2 · 1 2
Write the mixed number
A. 5
3
as an improper fraction.
1
·5
= 2
5 3
1
= 2
3
Simplify.
Multiply numerators.
Multiply denominators.
Additional Example 3C: Multiplying Mixed Numbers
Multiply. Write the answer in simplest form.
C. 6
2
3 ·
4
2
5
Write the mixed number
as an improper fraction.
4
= 20 · 22
3
5
Simplify.
1
= 88 or 29 1
3
3
Multiply numerators.
Multiply denominators.
Try This: Example 3B
Multiply. Write the answer in simplest form.
B. 3
3 ·
6
1
1
3
7
2
= 21 · 4
3
6
3
1
=
14 Or 4 2
3
3
How Do We Divide Fractions?
Dividing Fractions
A contractor wants to build a subdivision on a
2 acre tract of land that he owns. The two
acres of land are to be divided into ¼ acre
lots. How many lots will there be?
¼ ¼
¼ ¼
¼ ¼
¼ ¼
So, 2 ÷ ¼ = 8
Big Rocks – Divide Fractions
1. Rewrite first fraction
2. Change divide to multiply
3. Flip second fraction
4. Follow multiplication rules
To find the reciprocal of a fractions, flip it!
A number times it’s reciprocal equals one
You need the reciprocal when dividing fractions!
EXAMPLES:
2
3
3
2
5
2½=
2
2
5
Examples of dividing fractions
KEEP
5
10
9
12
SWITCH
1
5
9
3
FLIP
4
X
12
4
2
10
6
3
2
Examples of dividing fractions
7
9
2
4
3 ½
FLIP
SWITCH
KEEP
2
7
2
1
X
4
9
14
9
5
1
9
2 ¼
Example 1
6
2
5
32
5
2 32
5
÷
2
2
7
÷
16
7
x
7
16 1
=
14
5
=
2
4
5
Example 2
1
1
9
10
9
1 10
3 9
÷
6
2
3
÷
20
3
x
3 1
20 2
=
1
6
Example 3
8
1
13
105
13
21 105
13
÷
5
÷
5
1
x
1
51
=
21
13
=1
8
13
Your Turn!!!
4
1
=
÷
5
2
4
2
x
=
5
1
3
15
5
5
5
2
= 6 x 2 =
÷
6
5
1
3
3
1
1
= 8 x 1 = 8
÷
8
3
1
2 12
Homework
Pg 144 #10-32 even
simplify & show work &
no improper fractions allowed
1.
6 divided by 3 ½ =
2.
4/5 divided by 2/5 =
3.
1 ½ divided by 3 ¾ =
4.
3 ½ divided by 1 ¾ =
5.
2 ½ divided by 2 ½ =
6.
5 1/3 divided by 4/9 =
Check your
answers
1.
6 divided by 3 ½ = 1 5/7
2.
4/5 divided by 2/5 = 2
3.
1 ½ divided by 3 ¾ = 2/5
4.
3 ½ divided by 1 ¾ = 2
5.
2 ½ divided by 2 ½ = 1
6.
5 1/3 divided by 4/9 = 12
Back to Quiz
Homework
Pg 138
#8-30 evens
Show your work
Of means to multiply
Lesson Quiz: Part 1
Multiply. Write each answer in simplest terms.
1. 1 · 5 5
8 6 48
2. 5 5 · 1 35 or 2 11
6 2 12
12
3. 5 1 · 1 2 17 or 8 1
10
3 2
2
4. 3 · 4 2 7
16
3 8