B2.3 Use mental math strategies, including estimation, to add and subtract whole numbers that add up to no more than 20, and explain the strategies used.
Activity 1: A Little Elevator Ride (1 More and 2 More, 1 Less and 2 Less, and Basic Number Facts Related to 0)
Materials
- game sheets A Little Elevator Ride
- one token per student (each student should have a different coloured token)
- a numbered cube with the indices 0, 1 and 2 (or a spinner)
Students play in pairs and start on the first floor of the apartment building. The student who plays first throws the numbered cube (or spins the spinner) and moves their token, if any, up to the upper floors of the building according to the number of the cube (+ 0, + 1, + 2). The students take turns throwing the cube and their token "takes the elevator". The first student to reach the top of the building wins the game. On the 19th floor, you must get +1 to win.
Variant
Students can also use numbered cubes with -0, -1, and -2 labels, and start at the top of the building and gradually work their way down the elevator. Teachers can also give the numbered cube with the +0, +1, and +2 labels. Once on the20th floor, students switch cube and use the one with the -0, -1 and -2 clues to go back down to the first floor. The student who reaches the bottom first wins the game. To win, you must get the exact number to get to 1.
Source : Guide d’enseignement efficace des mathématiques de la maternelle à la 6e année, p. 72.
Activity 2: Hide-and-Seek (1 More and 2 More and Basic Number Facts Related to 0)
Materials
- a game sheet Hide the box
- wooden sticks, each with a number from 0 to 12 written on one end
- a cup
- a spinner where the indices +1 and +2 appear
- tokens
For this game, students are in groups of two or four. The student who plays first draws a stick from the cup (the numbered end of the sticks is placed down in the cup so that the numbers cannot be seen). The student spins the spinner and the resultant number is added to the number on the stick. The student looks at the game sheet to see if the resulting number is available on their side. If the number is available, a token is placed on that square. The stick is returned to the cup for the next round. The next player chooses a stick, spins the wheel, finds the sum of the numbers and places a token on the corresponding number on their side of the game sheet. The game continues in this manner until one of the players has hidden all the squares on their side of the game sheet.
Variant
Write higher numbers on the sticks or use a spinner that combines the +0, -0, +1, -1, +2, -2 strategies.
Source : Guide d’enseignement efficace des mathématiques de la maternelle à la 6e année, p. 73-74.
Activity 3: Hurry to School! (Doubles)
Materials
- a game sheet Hurry to school!
- 10 tokens for each student playing the game
- a ten-sided numbered die (or a spinner)
For this game, students work in pairs. Each student takes 10 tokens and places them on their side of the game sheet, one token per house. When all the tokens are placed, the student who starts the game throws the die and says out loud the number that is double the number on the die. If the house corresponding to that number has a token, the token is removed and placed in the centre of the game sheet in the "Hurry to School!" space. If the student throws the die and gets a number that has already appeared and the house is empty, they must wait until the next turn to try again. The next student to play throws the die, gives double the number that came up, removes the token from the corresponding house and places it in the centre of the game sheet. The game continues in this manner until a student has removed all of their tokens from the houses and sent the children to school.
Source : Guide d’enseignement efficace des mathématiques de la maternelle à la 6e année, p. 75-76.
Activity 4: Aim for the Doubles (the +1 Doubles)
Materials
- a spinner
- a game sheet Aim for the Doubles!
- 20 tokens
Students work in pairs. The student who plays first spins the spinner, doubles the number and adds 1. If the square with that number is free on their side of the game sheet, a token is placed there. If there is already a token, the student skips their turn. The game continues until a student has filled their side of the game sheet.
Source : Guide d’enseignement efficace des mathématiques de la maternelle à la 6e année, p. 77.
Activity 5: Ten or More Boxes (Grouping by Tens)
Materials
- Ten or More Boxes game sheets (one sheet per student)
- tokens
- a ten-sided numbered die (or a spinner)
- number cards (8, 9, 10) (eight cards of each number)
- a 1¢ coin
For this activity, students work in pairs. Each student has their own game sheet. A card is drawn from the pile of number cards and both students represent that number on their ten frame. Students take turns tossing the number cube (or spinning the spinner) and adding the number that comes up to their number on the ten frame. To determine who wins the round, students flip a coin. If it's heads, the student with the highest number gets a point and if it's tails, the point is given to the student with the lowest number. The student who gets 7 points first wins the game.
Source : Guide d’enseignement efficace des mathématiques de la maternelle à la 6e année, p. 78.