tuesday 9/2 quick review n. review video improper and mixed fractions
TRANSCRIPT
Example 1
58
x 34 =
1532
There are no common factors for 15 and 32, so this fraction cannot be simplified.
Example 2
3
4x
29 =
636
This fraction can be reduced. Divide the numerator and denominator by the GCF, which is 6.
= 16
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.
45
x 201 = 80
5 = 16
Another Example
15 x 161 = 15
615 and 6 have a GCF of 3.
=52
Five halves is improper, so we divide the bottom into the top.
2 52
41
2 12
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
57
x 816
In the second fraction, 8 and 16 have a GCF of 8.
8 ÷ 8 = 1 and 16 ÷ 8 = 212
Now, multiply with the simpler numbers. 5 x 1 = 5 and 7 x 2 = 14.5
14
Example 2
2
3x 5
12
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.
16
Now, multiply:
518
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
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?”
So, 3 ÷ ¼ = 12.
If you start with 3, you will have 12 groups of 1/4 .
1 2
3 4
5 6
7 11
10
12
9
8
Dividing a Whole Number by a Fraction
Can you see how you could manipulate the fractions to get an answer of 12?
Dividing a Whole Number by a Fraction
So, 5 ÷ 1/3 = 15.
If you start with 5, you will have 15 groups of 1/3 .
What is 5 ÷ 1/3?
Can you see how you could manipulate the fractions to get an answer of 15?
Steps….
1) Make the whole number a fraction by putting a 1 in the denominator
2) Keep the first fraction the same
3) Change the division sign to multiplication
4) Flip (take the reciprocal) of the second fraction
5) Now you use Multiplication Steps
Vocabulary: Reciprocal
When you flip the second fraction, you are writing that fraction’s reciprocal.
35
53
To Divide Fractions by Fractions: Rewrite the first fraction. Change the division sign to a multiplication
sign. Flip the second fraction upside down. Multiply.
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