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Title: Multiplying and Dividing Decimals Review

1
Multiplying and Dividing Decimals Review
In this section we are going to review
multiplying and dividing decimals.
Algebra 1A by Gregory Hauca Glencoe
Linda Stamper
2
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3
Multiply decimals as you would whole numbers.
Then place the decimal point in the answer
(product). To do this, add the number of decimal
places in the numbers being multiplied (factors).
Ex.1
Multiply the decimals.
1. Rewrite the problem vertically.
2. Multiply.
Do NOT line up decimal points.
3. Place the decimal point in the product. Add
the number of decimal places in the factors.
Write decimal points clearly!
4
When you multiply with a decimal, you may have to
write one or more zeros to the left of the answer
before you can place the decimal point.
Ex.2
Multiply the decimals.
1. Rewrite the problem vertically.
2. Multiply.
3. Place the decimal point in the product. Add
the number of decimal places in the factors.
5
Class Practice
Ex.4
Ex.5
Ex.3
6
When you divide a decimal by a whole number, the
decimal point in the quotient goes directly above
the decimal point in the dividend.
Ex.1
divide the decimals.
1. Rewrite the problem in standard division
format.
2. Place the decimal point in the quotient,
directly above the decimal point in the dividend.
3. Divide.
Write decimal points clearly!
7
To divide with a decimal divisor, move the
decimal to make the divisor a whole number. Then
move the decimal in the dividend by that same
number of places.
Ex.2
Multiply the decimals.
1. Rewrite the problem in standard division
format.
2. Move the decimal in the divisor and the
dividend to obtain a whole number divisor.
3. Place the decimal point in the quotient,
directly above the decimal point in the dividend.
Then divide
Write decimal points clearly!
8
Class Practice
Ex.3
Ex.4
9
Multiplying and Dividing Fractions Review
In this section we are going to review
multiplying and dividing proper and mixed number
fractions.
Algebra 1A by Gregory Hauca Glencoe
Linda Stamper
10
To multiply two fractions, multiply the
numerators to get the numerator of the product
and multiply the denominators to get the
denominator of the product.
Example
Ex.1
1. Multiply numerators and denominators.
11
When multiplying fractions simplify any numerator
with any denominator before multiplying the
numerators and denominators.
Not this...
Do this...
Ex.2.
1. Simplify first any numerator and denominator.
2. Multiply numerators and denominators.
12
Ex.3
1. Simplify first any numerator and denominator.
2. Multiply numerators and denominators.
Do not simplify the two 3s. You may NOT simplify
two numerators together or two denominators
together.
13
When multiplying mixed number fractions first
change the mixed numbers to improper fractions.
Then multiply.
Ex.4
1. Rewrite as improper fractions.
2. Simplify first when possible by reducing.
(Dividing by the Greatest Common Factor.)
3. Multiply numerators and denominators.
14
Ex.5
1. Rewrite as improper fractions.
1. Rewrite as improper fractions.
2. Simplify first when possible by reducing.
(Dividing by the Greatest Common Factor.)
2. Simplify first when possible by reducing.
(Dividing by the Greatest Common Factor.)
3. Multiply numerators and denominators.
3. Multiply numerators and denominators.
15
Class Practice
Ex.7
Ex.6
Ex.8
Ex.9
16
When we multiply a fraction by a fraction we
multiply the numerators and the denominators to
get the resulting product.
To divide a fraction by a fraction we need to
change the fraction division to an equivalent
fraction multiplication.
We do this by multiplying the first fraction by
the reciprocal of the second fraction.
Example
17
Ex.1
1. Change the division to a multiplication and
the second fraction to its reciprocal.
2. Reduce first and multiply.
18
To divide mixed number fractions we need to first
convert the mixed numbers to improper fractions.
Then we follow the same steps we learned to
divide simple fractions.
Ex.2
1. Convert mixed numbers into improper fractions
2. Change the division to a multiplication and
the second fraction to its reciprocal.
3. Multiply and simplify.
19
Ex.3
Ex.4
20
Class Practice.
Ex.5
Ex.6
Ex.7
21
Homework
• HW1A5 Handout
Decimal/Fraction Review B

22
WHITEBOARD PRACTICE.
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