How Many Slices Are Left?
Students will be able to solve subtraction problems using numbers 0–5.
- Gather the students together and display the pizza. Say, "This is a pizza. What kind of pizza do you like?"
- Have students turn and talk to share their favorite kind of pizza with a partner.
- Say, "Today we are going to learn about subtraction. We'll be using this pizza to help us."
Explicit Instruction/Teacher modeling(5 minutes)
- Point to the pizza and say, "Last night I made a delicious pizza for dinner. I want to see if there is any left for me to eat for lunch today. Does anyone have any idea of how I might figure out if there is any pizza left?"
- Allow for a few minutes of conversation between peers or as a whole class. Say, "Right! First I need to know how many pieces of pizza are left. Let's start by learning how many pieces I ate with my family last night."
- Display the pizza and show the five pieces. Remove three of the pieces and tell the class that three pieces were eaten last night.
- Model how to figure out finding the difference by thinking aloud. "I started with five pieces, then three of them were eaten (remove the 3) and now I have how many pieces left? One, two. Okay, so I have two pieces of pizza left over. That is what I can eat for lunch today!"
- Explain to the class that you just solved a subtraction problem. Subtraction is when we take one thing away from another thing and find out what is left.
- Draw the problem using numbers (5 – 3 = 2) and demonstrate how to read the problem aloud while explaining the symbols.
Guided Practice(10 minutes)
- Tell the class that you are going to practice solving another subtraction problem using your pizza and this time you need their help.
- Display the pizza again (as a whole) and say, "I made my mom a pizza for dinner. She ate 2 slices. How many slices does she have left?"
- Write the problem, 5 – 2 = ____, on the board and read it aloud with the students echo reading after you.
- Pair students up with a partner and ask them to solve the problem using the materials provided and to record their answers. Then pass out math manipulatives, paper, and pencils to each pair.
- Call the group back together and have several pairs share out their answer and how they got to their answer (ask guiding questions such as, "How do you know there are 3 slices left? Can you show us how you figured it out? What materials did you use?"
- Applaud the hard work of the class and tell the students that there are many different strategies or ways to solve a subtraction equation.
Independent working time(15 minutes)
- Explain to the class that now they will get to practice solving some subtraction problems on their own.
- Display the Outer Space Subtraction worksheet and review the instructions.
- Pass out worksheets, math counters, and pencils to each student.
- In a smaller group, review the numbers 0–10 with students using echo counting, songs, and games.
- Pass out number lines and/or hundreds charts for students to reference.
- Focus on one or two specific strategies for students to use when solving subtraction equations (e.g., crossing out the amount to be subtracted when using pictures).
- Review and/or introduce students to subtraction equations in the standard format (6 –2 = 4) and have them solve subtraction problems within 5.
- Encourage students to practice solving subtraction equations involving numbers to 10.
- Ask students to solve problems using additional strategies (e.g., using a number line, math counters, drawing pictures, etc.).
- Take note of students process and areas of confusion throughout the lesson. Check that students able to count using one to one correspondence, are able to keep track of the two parts of the equation, and are reading the subtraction equation correctly. Note if any students are mixing up addition or adding with subtraction.
- At the end of the session, collect student work samples and check for accuracy and areas of confusion.
Review and closing(5 minutes)
- Gather the class back together and provide one last group subtraction practice, emphasize a strategy you noticed students doing (using a number line, drawings and crossing out, etc.).
- Close by saying, "You all worked so hard on your subtraction problems!"