Mathematics Lesson Grade 3: Money: Adding Decimals

1. Mathematics LessonGrade 3: Money: Adding Decimals By: Mandy Wood

2. Let’s Learn How to Add Numbers with Decimals Now that you know how to add whole numbers, learning how to add decimal numbers will be a piece of cake! First, we will begin with a review of how to add one, two, and three digit numbers. Remember the rules for carrying! Try this worksheet: Review WS

3. Great! Now that you have successfully completed your review sheet, let’s move on to adding decimals. What exactly is a decimal you might ask? A decimal is a point or period like this: . It represents a part of a whole number. For example, the number 2 is less than the number 2.2. “2.2” is read “two and two tenths.” The number equals two whole ones, and two tenths of a one.

4. Hundreds, Tens, Ones, Tenths, Hundredths Let’s go back to what we know about how numbers are categorized. Numbers are divided into ones, tens, and hundreds. They are also divided into smaller parts. Ten “tenths” equal a single “one.” One hundred “hundredths” equal a single “one.” Because numbers go on forever, there can be numbers called ten millions or ten-millionths. That is a lot of numbers! The decimal goes here!

5. Decimals are Everywhere! When do you come in contact with adding decimals? Here are some examples: • Money ($1.40 + $0.25 = ?) • Weight ( .2 lbs + 1.2 lbs = ?) • Measurements ( 1.1 m + .05 m = ?) • Other numbers that represent parts of a whole can be written in decimal form. For example, half (½) of a pizza can be written .5 because ½ = .5

6. Money • Adding money is a great way to practice adding numbers with decimals. First, let’s review the value of each coin!

7. Pennies • A penny equals 1 cent. We write this as one hundredth of a dollar or $.01

8. Nickels • A nickel equals 5 cents. We write this as five hundredths of a dollar or $.05

9. Dimes • A dime equals 10 cents. We write this as one tenth of a dollar or $.10

10. Quarters • A quarter equals 25 cents. It is ¼ or one-quarter of a dollar. We write this as two tenths and five hundredths of a dollar or $.25

11. Dollars • In our lesson, we will use one, five, and ten dollar bills. This is what they look like: $5 Bill $1 Bill $10 Bill

12. Buy It with the Little Farmer! • Try this game to practice counting money. You will need to know how to count and add the correct amount of dollars and change for the upcoming activity! Buy It with the Little Farmer Game

13. Adding Decimals Adding decimals is really no different from adding whole numbers. First, line up the numbers vertically (up and down) as you normally do. 1 $ 21.04 $ 21.04 + 6.78+ 6.78 $27 82 The only thing you have to do differently is to position the decimal. Make a straight line down that connects the two decimals and the third one that will be in the sum. Now, add as you normally would! Don’t forget to add the dollar sign at the front of the sum! Great job! Now Add Don’t forget the dollar sign!

14. Activity Time • For this activity you will need either real or play money, or you will need to print off your own money online. • Here is a good website for printing off your own sheets of money: • MoneyInstructor.com Next Page

15. Supply Store Activity • Materials: erasers, pencils, pens, notebooks, crayons, and other classroom objects • Have the class create their own “supply store.” The teacher will write the prices of the objects on the board. Students will take turns being the cashier and the customer. The customer practices adding decimal numbers by adding up his or her items and paying for them, and the cashier’s job is to check his or her answer to see if it is correct! Students will love this simulation because they get to use money to buy and sell! No calculators – only pencil and paper!

16. Closure/Assessment • After the fun activity, we are going to do a worksheet to test our new skills in adding decimal numbers! Click below for the worksheet! • Adding Decimals Worksheet • Teacher Resource for Teaching Money