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Learning Objectives

Students will:

• Use "apples" to model the action in teacher created story problems
• Understand how to organize a subtraction number sentence with teacher guidance
• Use appropriate mathematical language to explain steps in creating number sentence based on apple tree picture created in SMART Notebook file.
• Represent subtraction word problems and their solutions as number sentences
• Use "apples" to model how to solve a subtraction sentence with manipulatives
• Apply crossing out strategy to solve word problems and number sentences.

Duration of Lesson

45 to 60-minutes to model/practice each strategy.

Description

In this lesson for first graders, students will learn about and practice different strategies (using manipulatives to act out a problem and crossing out) for subtraction. It is suggested that the children first be exposed to subtraction using tactile activities before moving to number sentences. Although there is opportunity for the students to work at the SMART Board, you may wish to have the students work with unifix cubes or other counters as you move through the slides to maximize student participation in the lesson.

Materials

• SMART Board set-up and SMART Notebook software
• Manipulatives such as cubes, counters, beans, etc. (whatever you readily have available)
• Individual whiteboard, markers, erasers OR paper, writing implement of choice OR number and operator cards (see support materials)
• Apple Subtraction file (see support materials)
• Subtraction Practice worksheet (see support materials)

Step-by-Step Procedure

(For most slides you can also have the students use cubes, etc. or writing materials at desks so all can act out the problems. By having them record answers on a whiteboard or paper or by using the number/operator cards, you can monitor how well they are grasping the concept.)

Anticipatory set: Explain to students that today they will be learning about (or practicing if you choose to use this lesson over multiple days) different ways to solve subtraction problems. Ask them to think about what happens when you take cookies off a plate. Do you have the same number of cookies or are there less cookies on the plate? That is what happens when we subtract.

Model with objects:
Step 1: Slides 2-4 provide opportunities for the teacher to model the action of subtraction and then relate it to the number sentence. The pull tab is connected to an apple which shows the actions to be taken. The trunk of the tree shows how many apples are on the tree - count to check with students. The sign on the basket tells how many apples to 'pick' off the tree. Once the apples are picked, count to see how many apples are left on the tree. The teacher can read the labels under the number sentence and ask the children if they know what number should be in the box. The answer is then revealed by erasing (or the teacher may just write it in if preferred).

Step 2: Slides 5-7 can be used by the teacher to create story problems (subtract from 8,6,9) that the children can act out using manipulatives at their seats and that individual students can complete at the SMART Board (in my own class I have a jar of popsicle sticks with the students' names that I randomly pick). By touching the blue die, you can change the number of apples picked from the tree. Depending on the ability level of the students, the teacher or students may complete the number sentence. It may help students to circle the important numbers in the story. (Note - To reset the page, move the top of the basket, place the apples back on the tree, and replace the top of the basket. Erase the numbers in the number sentence and the page can be used again.)

Step 3: Slide 8 introduces the next task, and Slide 9 provides an opportunity for the children to create the story and number sentence. Multiple children can work together (one for each step). First, the child decides how many apples to pick and place in the basket to take home and then writes the number in the appropriate box. Next, the child decides how many apples s/he would like to eat, places those apples on the hand, and writes the number in the appropriate box. Finally the child places the apples that were left in the basket on the plate and writes the number in the appropriate box. The class can then read the number sentence. End by placing the numbers in the appropriate part of the story and read together. The page can be reset by placing the apples back on the tree and erasing the numbers.

Crossing out strategy:
Step 4: Slides 10 & 11 introduce the crossing out strategy. Slides 12 & 13 allow for practice of the strategy. The students drag apples and cross them out to subtract.

Step 5: Slide 14 models drawing circles (more abstract) and crossing out to solve story problems. Slide 15 shows how the strategy can be applied to subtraction number sentences. Slide 16 allows for practice. The students can use the marker or the shape tool to make circles and cross out to subtract. Slide 17 is a matching activity. The students will draw lines between the equations and pictures on the SMART Board. By pulling the tab, a box is moved that reveals the answers.

Closure: At the end of the lesson, have the students explain in their own words how they can solve a subtraction problem. They should include the steps they need to take.

You can include subtraction practice worksheets from you own district math curriculum or that you create as well as the sheet attached to this lesson for independent practice. BrainPOP, Jr. has a video on basic subtraction in the math section which reviews various strategies for subtraction. (Visit: www.brainpopjr.com - subscription required)

Assessment

Monitor students as they work at the SMART Board and explain thought process.
Monitor students as they work at desks with manipulatives.
Completion of worksheet.

Support Materials

• SMART Notebook file: apple subtraction.notebook
• Worksheet file (pdf file): Subtraction Practice Sheet.pdf
• Number and operator cards (Word format): number and operator cards.doc

Related Academic Standards

New York State

1.OA.1 Use addition and subtraction within 20 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.

1.OA.2 Solve word problems that call for addition of three whole numbers whose sum is less than or equal to 20, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.

1.NBT.4 Add within 100, including adding a two-digit number and a one-digit number, and adding a two-digit number and a multiple of 10, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used. Understand that in adding two-digit numbers, one adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten.

1.NBT.5 Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.

MST3.1.N.24 Students develop and use strategies to solve addition and subtraction word problems.

MST3.1.N.25 Students represent addition and subtraction word problems and their solutions as number sentences.