Transcript Multiplying Fractions

Warm Up
Warm Up
Write each number as an improper fraction.
1.
2 1
3
4.
62
3
7
3
20
3
2.
7
1
8
5.
53
8
15
8
43
8
2
3. 3
5
17
5
Multiplying Rational Numbers
Section 2.4
Objectives
• Multiply rational numbers and take positive
rational numbers to whole-number powers.
(NS 1.2)
In words
• To multiply two fractions, multiply the
numerators to get the numerator of the
product and multiply the denominators to
get the product.
3 1 3 1 3
 

4 5 4  5 20
Multiplying
Fractions
• Multiply numerators &
denominators.
• Simplify if needed.
5 3
 
8 2
 15

16
53
8 2
Multiplying
Fractions with
Mixed Numbers
Rewrite as improper
fraction.
Multiply numerators
& denominators.
Simplify.
2 4
5 19
1 3 

3 5
3 5
5 19

3 5
19
1
or 6
3
3
If you
can,
cross
cancel!
Try these on your
own…
6
7 =
1
8
3
5
3
28
–
=
2 1
4
3 2
–3
5
8
= 3
8
–
7 4
8 7
=–
1
2
Application
1
Mark runs
mile each day. What is the
7
total distance Mark runs in 5 days?
1 (5) =
7
=
=
1 5
7 1
1•5
I7 • 1
5
7
5
Mark runs 7 mile in 5 days.
How do you multiply fractions?
Multiplying by a
Whole Number
Rewrite 10 as fraction
Multiply numerators and
multiply denominators.
6x
10 
5
6 x  10 2
6x  2

5 1
1
Reduce top and bottom
Simplify
6 x 10

5 1
12 x
Multiplying
Decimals
•To multiply decimals, first
multiply as you would with
integers.
•The number of decimal
places in the product is equal
to the sum of the number of
decimal places in the
factors.
Multiplying
Decimals
A. 2(–0.51)
2
 –0.51
–1.02
0 decimal places
2 decimal places
0 + 2 = 2 decimal places.
B. (–0.4)(–3.75)
2 decimal places
–3.75
1 decimal place
 0.4
2 + 1 = 3 decimal places
1.500
or 1.5
Try these on your
own…
A. 3.1(0.28)
3.1
 0.28
0.868
B. (–0.4)(–2.53)
–0.4
 –2.53
1.012
Let’s practice
5 3
 
9 10
2
3
1 2 
3
9
 7x
 60   140 x
3
1
6
8
3
9
2
1
3
3  2  30
5 8
5
 5x 7
 1x
 
9
21 15
7
1
2
1 2  2
10
8
5
How you do you multiply
decimal?
Lesson Quiz
12
7
1. 9 1
7
2.
2
3
–5
8
3. –0.47(2.2)
–
5
12
–1.034
4
1
2
4. Evaluate 2 (x) for x = .
5
2
8
Edgar runs 9 mile each day. What is the total
distance that Edgar runs in a 7-day week?
2
6 miles
9