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 necessary to 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 0.889.650.88

7720 77200

8.4920

First Estimate10

1

10The product will be less than 10

since both estimates are

larger than the original factors.

Two to the leftTwo to the left

Four to the left

plus

Moving the decimal point

5.12 x 0.5

5.12 0.5

2.560

First Estimate 5

1

5The 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

two to the left

one to the leftthree to the

left

plus

Moving the decimal point

63.7 x 2.9

63.7 2.9

5733 12740

First Estimate64

3

192The product will be less than 192

because both estimates for

the factors are greater.

One to the left

one to the left

two to the left

plus

184.73

Moving the decimal point

0.043 x 0.06

0.043 0.06

.00258

First Estimate 0

0

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

Three to the leftTwo to the leftFive to the left

plus

Moving the decimal point

Practice On Your Own4.37 x 0.39

45.2 x 0.009

7.35 x 8.27 x 1.2

Practice ANSWERS4.37 x 0.39 = 1.7043

45.2 x 0.009 = 0.4068

7.35 x 8.27 x 1.2 = 72.9414

ASSIGNMENTO Fold paper to make four boxes on each

side. This will be your worksheet to turn in for a progress grade.

O Complete problems in Holt math book on page 1323rd and 6th period: complete problems 33–404th and 5th period: complete problems 29–36

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

O 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).