Growth Point 5

Materials: None.

Activity: This task is a useful means of assessing what the students know about different strategies to use when adding and subtracting numbers. Explain to the students that a new student has arrives at their school from Chonk Rock, a faraway planet (see Place Value growth point 2: ‘Chonks’). Chonks know nothing about the way we work at school, so your teacher has asked you to help teach the new Chonk student some of the things you know about Maths. Each group is asked to put on a short play to dramatise one of the addition or subtraction strategies that can be used.

The strategies to be presented are:

• doubles

• commutativity

• adding ten

• tens facts

• near doubles

• adding nine

• build to next ten

• fact families.

Use your play to show how these strategies might be useful in everyday life on Earth.

Related key ideas: Properties of addition, properties of subtraction.

Materials: Dominos

Activity: If students have not used dominoes before, explain to them that dominoes have pips (or dots) on them which represent a value. When playing dominos, you can join two together if they have the same number of pips on the two ends that are joining. Challenge the students to make a domino train which has a total value of 10, 20, 30, 40 or 50 pips. For any of the above ask, ‘Is there more than one solution?’ ‘What is the longest/shortest train you can make?’.

Related key ideas: Part-part-whole, partitioning, properties of addition, combining.

Materials: Two red dice and two blue dice, and one calculator (optional) for each pair.

Activity: One student rolls the blue dice and adds the two numbers together to find the total (e.g. rolls 4 and 3, and has a total of 7). The other student then rolls the two red dice and uses the numbers to make a two-digit number (e.g. rolls 5 and 3, so can make either 35 or 53). Working together, the students then add the number from the blue dice and the number from the red dice, using an appropriate strategy. Record the answer, and check with a calculator if desired. On the next turn, students swap tasks. Then have whole class discussion about the highest number calculated by a group, and the strategies used.

Related key ideas: Properties of addition, properties of subtraction, combining, partitioning, separation, comparison.

Variation:

• Students subtract the total found on the blue dice from the two-digit number created by the red dice.

• Rather than add the two dice together, make two two-digit numbers that can be added or subtracted.

• What is the highest total that could be scored? What is the lowest total that could be scored? How do you know this?

Materials: A set of playing cards (picture cards removed)

Activity: Shuffle a deck of cards. Deal five cards to each player and deal four extra cards face up in the middle. Teacher determines a target number that is appropriate for the students. Students take turns using the cards they have in their hands and one that is in the centre to make the target number. Each round, students collect an additional card from the left-over deck. Students record their solutions on whiteboards.

Related key ideas: Part-part-whole, partitioning, properties of addition, combining, properties of subtraction.

Variation: Students use a combination of addition and subtraction to find the target number.

Materials: A set of playing cards with picture cards removed.

Activity: A student draws two cards from the deck and creates a two-digit number using the cards (e.g. if the student draws 6 and 1, they can make 16 or 61). The student then draws a third card from the deck. If it is an even number, they add it to their total. If it is odd, they subtract it. After five rounds, the teacher decides whether the winner is the player with the highest or lowest total (depending on the focus).

Related key ideas: Combining, separation, comparison part-part-whole, partitioning, properties of addition, properties of subtraction.

Materials: A set of playing cards with picture cards removed.

Activity: Shuffle a deck of cards and deal out nine cards in a 3 × 3 array. Say ‘I spy with my little eye two cards that add to a total of x. What could they be?’. Students use whiteboards to list any of the solutions they can see. Repeat the process with similar questions. Once the students are familiar with the game, invite them to come up with ‘I spy’ statements they can pose to the class.

Related key ideas: Part-part-whole, partitioning, properties of addition, combining.

Materials: Dice.

Activity: In pairs, students roll a dice six times and keep a running total as they go. The student with the highest total at the end of six rounds is the winner.

Related key ideas: Part-part-whole, partitioning, properties of addition, combining, properties of subtraction.

Variation: Start with a total of 20, 50 or 100 and subtract the quantities rolled. Student who has the lowest total after six rolls wins.

Materials: Dice.

Activity: Students roll the dice eight times to get a string of numbers, and record them. The students then use a variety of mental strategies to add the numbers and record their solutions. The aim of this game is to find the most efficient solution. Once students have found the most efficient solution, they must try to convince another group of students or the teacher that they are correct.

Related key ideas: Part-part-whole, partitioning, properties of addition, combining.

Materials: Calculator.

Activity: A student types a two-digit number into the calculator and hands it to their partner. The partner then decides how many more they need to add to get to 100 and enters it into the calculator to check. Players then swap.

Related key ideas: Combining, part-part-whole, partitioning, properties of addition.