Step By Step Decimal Subtraction
Students will be able to subtract decimals to the hundredths place.
- Review decimal basics by writing a decimal number to the tenths place on the board (e.g., 2.4).
- Call on a student to read the number and tell you the value of the number in the tenths place (four-tenths). Tell students that the Tenths placeIs the first digit to the right of the decimal point and represents one out of ten equal parts of a whole.
- Write a decimal number to the hundredths place on the board (e.g., 4.56).
- Call on a student to read you the number and tell you the value of the number in the hundredths place (six hundredths). Tell students that the Hundredths placeIs to the right of the decimal point and represents one out of one hundred equal parts of a whole.
- Tell students that today they will practise subtracting decimals.
Explicit Instruction/Teacher modeling(10 minutes)
- Explain to students that, in order to subtract decimals, they must follow four steps.
- Post a piece of chart paper on the board to be used as a reference throughout this lesson. Title this chart paper "Subtracting Decimals" and write the four steps for subtracting decimals.
- Write: "Step 1." Line up the decimals vertically.
- Model for students how to line up 4.56 and 2.4 vertically so that the numbers are one right under the other and the decimal points are lined up.
- Write: "Step 2." Add a zero (placeholder) to the right of any numbers as needed.
- Model for students how to add a zero to 2.4 to make it 2.40 so that the two numbers have the same number of digits.
- Write: "Step 3." Beginning in the lowest place value, begin subtracting from right to left.
- Model for students how to subtract 2.40 from 4.56.
- Write: "Step 4." Bring down the decimal.
- Model for students how to bring down the decimal to get 2.16.
- Tell students that they may encounter equations where they will need to regroup to complete the subtraction equations (e.g., 5.5 – 3.07).
Guided practise(15 minutes)
- Show students a copy of the Subtracting Decimals worksheet on the document camera.
- Tell students that this worksheet contains subtracting decimal equations with decimals to the tenths and hundredths place.
- Model for students how to use the four steps for subtracting decimals to complete the first row of equations. Point to and reference the chart paper as you move through each step.
- Distribute a copy of the Subtracting Decimals worksheet to each student.
- Assign students into effective partnerships and tell students to complete the remainder of their worksheet with their partners.
- Circulate and offer support.
- Call students together as a whole class to go over the answers and answer any questions that may have arisen.
Independent working time(10 minutes)
- Tell students that they will now practise this skill independently.
- Preview and distribute the Decimal Subtraction worksheet.
- Remind students to use the Subtracting Decimals chart paper as a reference when they are completing this worksheet.
- Circulate and offer support as students are working independently.
- Pre-teach a lesson on regrouping.
- Write out the Subtracting Decimals four steps on individual pieces of paper to distribute to students to keep at their desks to use throughout the lesson.
- Provide students with a partially completed copy of the Decimal Subtraction worksheet during Independent Work Time.
- Gather students into a teacher-led small group to complete the Decimal Subtraction worksheet with support during Independent Work Time.
- Challenge students by providing them with the Delicious Decimals worksheet to practise subtracting equations with decimal numbers in the thousandths place (see optional materials).
- Provide students with the What's Up, Decimals? worksheet to solve two-step word problems involving adding and subtracting decimals (see optional materials).
- Encourage students to create their own subtracting decimals worksheet to exchange with a partner. Challenge students to include equations with decimal numbers in the thousandths place.
- Distribute whiteboards to each student.
- Write a subtraction equation with decimals to either the tenths or hundredths place on the board.
- Tell students to solve this equation on their whiteboards.
- Instruct students to hold up their whiteboards so you can see their answers.
- Continue this process with at least four more equations.
Review and closing(5 minutes)
- Tell students that learning to subtract decimal numbers is a valuable skill that they will practise both in and out of school.
- Ask students to brainstorm with a partner a time when they might encounter subtracting decimal numbers in real life (e.g., subtracting money when shopping at a grocery store or subtracting the number of miles left to drive in a road trip).
- Call on pairs to share their ideas with the whole class.