Fraction Multiplication and the Products of Decimals

Lesson 11 Student Outcomes

• students learn how to use estimation and place value to determine the placement of the decimal point in products and to determine that the size of the product is relative to each factor.
• Students discover and use connections between fraction multiplication and decimal multiplication.
• Students recognize that the sum of the number of decimal digits in the factors yields the decimal digits in the product.

Exploratory Challenge

You will not only solve each problem, but your groups will also need to prove to the class that the decimal in the product is located in the correct place. As a group, you will be expected to present your informal proof to the class.

1. Calculate the product. 34.62 x 12.8

2. Xavier earns $11.50 per hour working at the nearby grocery store. Last week, Xavier worked for 13.5 hours. How much money did Xavier earn last week? Remember to round to the nearest penny.

The number of digits after the decimals in the factors tells us how many digits after the decimal in the product.

Exercises 1 - 4

1. Calculate the product. 324.56 x 54.82

2. Kevin spends $11.25 on lunch every week during the school year. If there are 35.5 weeks during the school year, how much does Kevin spend on lunch over the entire school year? Remember to round to the nearest penny.

3. Gunnar's car gets 22.4 miles per gallon, and his gas tank can hold 17. 82 gallons of gas. How many miles can Gunnar travel if he uses all of the gas in the gas tank?

4. The principal of East High School wants to buy a new cover for the sand pit used in the long jump competition. He measured the sand pit and found that the length is 29.2 feet and the width is 9.8 feet. What will the area of the new cover be?