# Get to the Point: Using Money to Teach Decimals

Math

4th and 5th

## Lesson Objective:

By the end of this lesson, your students about decimals through the use of money allowing them to have a real-world application for this lesson.

## Common Core Standards:

• 5.NBT.1 "Recognize that in a multi-digit number, a digit in one place represents 10 times as much as it represents in the place to its right and 1/10 of what it represents in the place to its left."
• 5.NBT.7 "Add, subtract, multiply, and divide decimals to the hundredths."

## Material Needed:

• Pennies, nickels, dimes, quarters, half dollar, paper/cardboard circles, or fake coins.
• Personal whiteboards and pens.
• List of Saturday jobs and purchase items. (Digital on the board or a physical paper given to each student.)
• Optional homework assignment. (Adding decimals when grocery shopping.)

## Lesson Starter:

Before you start on decimals, complete a quick review of fractions and how to turn whole numbers into decimals:

1. Ask your students how to write half of something. (Use their whiteboards and pens to show you their answers. Ex. 1/2)
2. Ask your students how else they could write half of something. (Use their whiteboards and pens to show you their answers. Ex. .5)
3. Next, get your students to think about food prices at the store. Point out that \$1.50 is one and a half dollars and show them how it's written.
4. Next, ask one student how old they are. (Wait for a reply.)
5. Say, "ok, you're nine, but not exactly nine, right?" Write nine on the board, add a decimal point, and determine their exact age using decimals. (Ex. If the student was born in June, and it is March, the student would be 9.75.)
6. Ask your students which side of the decimal point holds the larger number. (Wait for replies.)
7. Tell them that the left is larger and the right is smaller. (Ex. 12.45; 12 is the large number, with the .45 being less than half of 1.)
8. Pass out 100 pennies or penny substitutes and have your students divide them in half.
9. Ask your students how many pennies are in each group of coins. (Students should have two groups of 50.)
10. Next, do a simple division problem to turn the 50 pennies into half of the 100 pennies. (Ex. 100 / 2 = 50; 50 / 100 = 0.5)
11. Repeat dividing the pennies into smaller groups, such as quarters, to drive home the process of dividing and decimals for each one and compare them to fractions. Remind them each is part of \$1.
• Penny group: 1c /100c = .01
• Nickel group: 5c /100c = .05
• Dime group: 10c /100c = .1
• Quarter group: 25c /100c = .25
• Half-dollar group: 50c /100c = .5

## Main Lesson:

1. Tell your students they now have a Saturday job. They may choose a job from a given list, such as:
• Mowing the lawn at \$2.00 per hour
• Washing windows at \$2.25 per hour
• House cleaning at \$2.50 per hour
• Provide at least five jobs for students to choose from.
2. Once they've decided on what job they want, let them choose what they will spend their earnings on from a given list, such as:
• Book: \$20
• Video game: \$50
• Movie ticket: \$10
• Provide at least five purchases for students to choose from.
3. Each student must determine how many hours (down to the decimal) they will need to work to pay for their chosen item. Point out that to find the answer, they have to divide the item they want to purchase by their pay per hour.
• Example: Washing windows at \$2.25 per hour to pay for a \$20 book. \$20 / \$2.25 = 8.89 hours
4. Continue to have the students practice finding the decimal using different jobs and purchase combos. Have students who understand the concept help their peers that are struggling.

## Lesson Feedback & Homework:

1. This is just a starter, as decimals get more complicated when the numbers are larger.
2. Ask your students if they can see why decimals are helpful when using money. (Wait for replies or student insight.)
3. Point out that math uses formulas that have strict rules. Once they have the rules, they are set.
4. Provide homework with a similar assignment, such as grocery shopping with a limited budget. There is no division for this assignment, have students add their decimals to find the total cost of their shopping trip.
1. Example: With a \$25 budget, students can purchase items X, Y, and Z for a total amount of \$XX.XX.

Written by Cathy Tomkinson
Education World Contributor