Multiplying Decimals

Objectives• Objective: We will find the product

of two decimals.

• Language Objective: We will use key words whole number, product, and decimal.

Word Definition Example

whole number a counting number from one to infinity

795489

decimal a number written as a whole number and a

part of a whole number

4.2four and two tenths

5.73five and seventy-three hundredths

product the answer to a multiplication

problem

9 x 6 = 54

Vocabulary

Steps for Multiplying Decimals

1. Line up the decimals as if they were whole numbers. (You DON’T have to line up the decimal point!)

2. Multiply as if the numbers were whole numbers.

3. Go back to the decimal and count the total number of decimal places to the right of the decimal points.

4. Move the decimal point that many places to the left of the product.

Multiplying Decimals

9.52 x 3.8

36.176

Multiplying Decimals

13.2 x 5.45

71.94

Multiplying Decimals

1.24 x 8

9.92

Multiplying Decimals

0.003 x 6.4

0.0192

Multiplying Decimals

7.49 x 1.02

7.6398

Multiplying Decimals

1.93 x 3.7

7.141

Multiplying Decimals

4.351 x 7.25

31.5375

Multiplying Decimals

2.45 x 2.81

6.8845

Multiplying Decimals

6.892 x 41.34

284.91528

Word ProblemsMarty runs tract at Mountain View High School in Tucson. He ran the 200-meter dash in 35.2 seconds. It took Jenny 1.2 times as long as Marty to run the 200-meter dash. How long did it take Jenny to run the 200-meter dash?

42.24 seconds

Word ProblemsZach bought 5.5 pounds of oranges for $0.90 per pound. How much did Zach spend on oranges?

$4.95

Word ProblemsKara weighs 74.6 pounds. Her mom weighs 1.8 times as much as she does. How much does Kara’s mom weigh?

134.28 pounds

Word ProblemsMary is buying candy for her birthday party. She bought 3.2 pounds of gummy bears for $1.25 per pound. She bought 5.75 pounds of M&Ms for $4.50 per pound. She bout 2.8 pounds of licorice for $2.99 per pound. How much money did Mary spend in all?

$38.25

ConclusionWhat is the most important thing to remember when multiplying a whole number and a decimal?

How is this different from adding decimals?