Flexible additive strategies - 2 digit numbers

This resource has been developed in partnership with the NSW Mathematics Strategy Professional Learning team, Curriculum Early Years and Primary Learners, and Literacy and Numeracy.

Using the resource

This resource is the second section of a four-part resource supporting additive thinking. Use this resource in conjunction with the other resources in this series in order to support a connected network of critical mathematical concepts, skills and understanding.

Supporting tasks

Full instructions on how to use each of these tasks, including materials, related tasks and learning intentions are included in the resource, available for download on this page.

Task 1: Let’s talk 1

Students view the ‘Let’s talk 1' video.

Task 2: Claim it

Students roll three dice and use addition and subtraction to match them to a set of numeral cards 0-27.

  • Variation 1: Play in larger teams

  • Variation 2: ‘Freeze’ the game between two players at a particular moment and involving the class in an investigation about what move to make next and what may happen as a result

  • Variation 3: Introduce a ‘free pass’ card

Task 3: Subtraction face off

Students use playing cards to form a 2-digit number and a 1-digit number then arrange the cards to make the smallest difference.

Task 4: Difference challenge

Students form small groups and use playing cards to form a 2-digit numbers The aim is to get 2 numbers with a difference of 45, or, at the end of 5 turns each, the student with a difference closest to 45.

  • Variation 1: Use a hundred chart to assist mental calculations

  • Variation 2: After creating the first two digit number, ask questions such as ‘What numbers would or wouldn’t like to draw next and why?

  • Variation 3: Change the challenge to addition of two 2-digit numbers with the goal of being as close as possible to 100. Encourage students to use their knowledge of part-whole to ten to work out solutions

Task 5: Strategic part-part-whole thinking

Students investigate different ways to partition numbers

  • Variation 1: Change the target number

Task 6: How might we?

Students use pencils to practice different grouping strategies

  • Variation 1: Plan for a class party and determine how many packets of 10 items (such as cups, spoons) would be needed for the class, discussing how many would be left over.

Task 7: Addition and subtraction table patterns

Students roll 2 large 1 – 10 dice record their results on an 11 x 11 addition and subtraction grid.

Task 8: How can we represent that?

Students work out as many ways as possible to solve the problem 23 + 38

  • Variation 1: Change the numbers used in the problem in order to examine the efficiency of different strategies

  • Variation 2: Students to model all possible strategies they can think of and reflect upon the efficiency of each


  • Teaching and learning

Business Unit:

  • Educational Standards
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