B2.4 Use objects, diagrams, and equations to represent, describe, and solve situations involving addition and subtraction of whole numbers that add up to no more than 50.
Activity 1: Addition and Subtraction Problems
Materials
- reusable plastic bags (one per student)
- wooden sticks (five per student)
- markers
- stickers
Give each student a plastic bag and five wooden sticks.
Have them decorate the sticks with markers or stickers to represent five characters.
Suggest that students use their characters to simulate the problems that will be presented to them.
Substitute the names in the stated problems with names of students in the class.
Sample Problem
James, Julie, and Corinne are thirsty. They go to the fountain to drink. How many people are at the fountain? Renee and Jamal also decide to go and drink. How many people are at the fountain now?
Write the corresponding number sentence on the board (3 + 2 = 5).
Suggest other such problems, including subtraction problems.
Invite students to act out the story by standing in a line near the reading or math corner, for example, or to illustrate the problem using the characters they have created.
Form teams of two and ask them to compose addition or subtraction problems featuring the characters created.
Invite them to present their problems to the class.
Source : Guide d’enseignement efficace des mathématiques de la 1re à la 3e année, p. 98.
Activity 2: Statement Problems
Materials
- Appendix 1SO.3 (Problem sheets)
- small objects (for example, tokens, cubes, buttons, bread bag clips)
Form small teams so that students can stage a problem in a team.
Provide small objects for students to represent problems with materials.
Select a problem from Appendix 1SO.3 (Problem Sheets) and read it to the class or project a copy and read it with students.
Ask one team to prepare to act out the problem while the others use the manipulatives to illustrate the solution.
Invite the team to present the problem and ask questions to clarify a point or check for understanding by the students watching.
Ask a few students to explain how they solved the problem using the materials.
Have students write a number sentence that represents the problem.
Source : Guide d’enseignement efficace des mathématiques de la 1re à la 3e année, p. 98-99.
Activity 3: The Refrigerator
Materials
- Appendix 1SO.4 (Refrigerator Model) (one copy per student)
- glue sticks (one per student)
- grocery store advertising flyers
Provide a copy of Appendix 1SO.4 (Refrigerator Model) to each student.
Guide students through the following steps to prepare the refrigerator or ask for volunteers to do so before the activity begins:
- Cut out the outline of the refrigerator.
- Cut the solid line separating the refrigerator from the freezer to the dotted line.
- Apply glue to the back of the narrow part of the refrigerator (between the dotted line and the outline) and glue it to a piece of construction paper.
- Trace the outline of the refrigerator on the construction paper and draw a line to separate the refrigerator from the freezer.
- Fold the doors along the dotted line to open them.
Cut out small pictures of food from grocery store promotional booklets.
Use the refrigerator to illustrate the concepts of decomposition and grouping in addition.
Suggest a number to write on the refrigerator magnet drawn on the door (for example, 8).
Have students place pictures of food elements behind the refrigerator (for example, 5 pictures) and freezer (for example, 3 pictures) doors to represent the number (8) written on the door.
Write a number sentence that represents the terms and the sum.
Assemble the students' illustrations to represent all the distributions of the number and create the "8" book.
Source : Guide d’enseignement efficace des mathématiques de la 1re à la 3e année, p. 99-100.
Activity 4: Hot Dog Cart
Materials
- Appendix 1SO.5 (Game Board - Hot Dog Cart) (one copy per student)
- Appendix 1SO.6 (spinner "plus/minus") (one spinner per team of two)
- small objects (about 40 per student)
- dice (one die per pair)
Prepare "plus/minus" spinners using Appendix 1SO.6.
Form teams of two and give each team a die and a plus/minus spinner.
Provide each student with a copy of Appendix 1SO.5 (Game Board - Hot Dog Cart) and approximately 40 objects.
Provide the following instructions:
- Place 15 objects on the board to represent people waiting in line to buy hot dogs.
- Rotate the plus/minus spinner to determine the operation to be performed.
- Roll the die to see how many people join or leave the line.
- Perform the operation by moving the objects.
- Take turns playing until one of the two lines disappears (because there is no one left) or the line reaches 30 or more people.
Enrich the task by asking students to create an addition or subtraction problem based on the hot dog cart. They can illustrate their problem on the game board.
Source : Guide d’enseignement efficace des mathématiques de la 1re à la 3e année, p. 100.
Activity 5: Numbers in the Water!
Materials
- cards numbered from 1 to 12
- illustration of a lake
- giant dice (three)
Directions
- Display numbers from 1 to 12 on the board or on an easel.
- Place an illustration of a lake under the numbers.
- The goal of the game is to put all the numbers in the water in order from 1 to 12.
- Roll the 3 giant dice and ask students to find a way (either by adding the numbers or subtracting them) to get a number to fall in the water.
Students can use two numbers or all three numbers obtained. For example, the target number is 5. The numbers rolled are 3, 6, and 2. Students can say 6 + 2 = 8, then 8 - 3 = 5, or simply 3 + 2 = 5.
Write the different student responses on the board.
If the target number cannot be found, roll the dice again. The game ends when all the numbers from 1 to 12 are in the water.
Questions to Ask
Before rolling the dice, ask students: What numbers would you like to get? Why?
Source : L’@telier - Ressources pédagogiques en ligne (atelier.on.ca).
Activity 6: Addition of Whole Numbers
Example 1
During recess, Mrs. Smith sees 7 children on the large play structure and 29 children playing ball. How many children does she see in total?
STRATEGY
Addition Using Anchor Point 10 and Compensation
I represent 29 and 7 using ten frames. The number 29 is close to 30, so I remove 1 from the frame with 7 tokens, leaving 6. I add the token to 29, which gives me another ten, so that makes 30. Now I have to add 30 and 6.
30 + 6 = 36
Example 2
In a garden, there are 47 flowers. 33 are tulips. The others are daffodils. How many daffodils are in the garden?
STRATEGY
Addition Using Composition
Using the Rekenrek, I represent the 33 tulips with 3 rows of 10 beads and 3 red beads on the4th row. I need to add the daffodil beads to represent 47 flowers.
I add the 7 beads from the4th row to get to 40. Then I add the 5 red beads and 2 of the white beads from the5th row to get to 47.
Afterwards, I add up all these added beads.
7 + 5 + 2 = 7 + 7 = 14
So, there are 14 daffodils in the garden.
Source : En avant, les maths! 1re, CM, Nombres, p. 3-4.
Activity 7: Subtraction of Whole Numbers
Example 1
Throughout the year in art Anne created 39 pieces of art. She has given some of her art to her family members. She has 22 pieces left. How many pieces of art did she give to her family?
STRATEGY
Add to Subtract Using a 50s Grid
On the 50s grid, I circle the number 39, which is the number of artwork pieces Anne has at the start. I circle the number 22, which is the number of artwork pieces she has left. From 22, I leap by 10, which is 32, leap by 5, which is 37, and leap by 2, which is 39.
\(\displaylines{\begin{align}22 + \mathord{?} &= 39 \\ 22 + 10 + 5 + 2 &= 39 \\ 22 + 17 &= 39\end{align}}\)
Anne gave 17 pieces of art to her family.
Example 2
Luke read 36 pages in his book, while Melissa read 12 fewer pages of the same book. How many pages did Melissa read?
STRATEGY
Subtract Using Place Values
I use the base 10 material to represent the 36 pages that Luke read. I take 3 sticks to represent 3 tens and add 6 small cubes (units) to represent 6 ones. From this amount, I take 1 stick and 2 units to represent the 12 pages that Melissa has not read. This leaves me with 2 sticks and 4 units, so 2 tens and 4 ones. Melissa has read 24 pages (36 - 12 = 24).
Source : En avant, les maths! 1re, CM, Nombres, p. 3-4.