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MULTIPLYING DECIMALS. EQ: What is the standard algorithm for multiplying decimals? MCC6.NS.3 ---Fluently multiply multi-digit decimals using the standard algorithm. What is a FACTOR?. A number that is multiplied by another number to get a product. What is a PRODUCT?.

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MULTIPLYING DECIMALS

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## MULTIPLYING DECIMALS

EQ: What is the standard algorithm for multiplying decimals?

MCC6.NS.3 ---Fluently multiply multi-digit decimals using the standard algorithm.

### What is a FACTOR?

A number that is multiplied by another number to get a product.

### What is a PRODUCT?

The ANSWER to a multiplication problem.

### When multiplying, is it necessary to line up the decimal points as you do with the addition and subtraction of decimals?

It is not necessaryto line up the decimal points when multiplying decimals.

### What is the standard algorithm for multiplying decimals?

1) Write down the original problem.

2) Ignore the decimal points and multiply.

3) For each factor, count the total # of places to the right of each decimal point.

4) Use the total number of places right of the decimal point (all factors) for the placement of the decimal point in the product. Start from the last digit in the product and move left.

### Let’s try some:

9.65 x 0.88

First Estimate

Moving the decimal point

10

1

9.65

0.88

Two to the left

plus

Two to the left

10

7720

77200

The product will be less than 10 since both estimates are larger than the original factors.

8.4920

Four to the left

5.12 x 0.5

Moving the decimal point

First Estimate

5

1

5.12

0.5

two to the left

plus

one to the left

5

2.560

three to the left

The product will be less than 5 because there is a greater increase in the estimate for 0.5 than decrease in the estimate for 5.12

63.7 x 2.9

First Estimate

Moving the decimal point

64

3

63.7

2.9

One to the left

plus

192

one to the left

5733

12740

The product will be less than 192 because both estimates for the factors are greater.

184.73

two to the left

### 0.043 x 0.06

First Estimate

Moving the decimal point

0

0

0.043

0.06

Three to the left

plus

Two to the left

0

.00258

Five to the left

The product will be less than 1 and closer to 0.

### Practice On Your Own

4.37 x 0.39

45.2 x 0.009

7.35 x 8.27 x 1.2

### Practice ANSWERS

4.37 x 0.39 = 1.7043

45.2 x 0.009 = 0.4068

7.35 x 8.27 x 1.2 = 72.9414

### ASSIGNMENT

• Fold paper to make four boxes on each side. This will be your worksheet to turn in for a progressgrade.

• Complete problems in Holt math book on page 132

3rd and 6th period: complete problems 33–40

4th and 5th period: complete problems 29–36

• First, copy the original problem on your paper, then solve. Please circle your answers.

• When you finish, please turn your work in, put the textbook back, and start on “What did Arf the Dog give his master for his birthday?” (on the table).