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• ### Where are they now?

Uses count on from larger (add 1, 2 or 3) or part-part-whole knowledge to mentally add small collections to one and two digit numbers

• ### Where to next?

Uses doubles and near doubles strategy to mentally add selected 1 and 2-digit numbers ( eg, 8 and 9, 15 and 16)

Use formal notation to record equations

• ### Where are they now?

Solves and poses ‘difference’ problems (1-10) using counting back (1, 2 or 3) from known or part-part-whole knowledge
ie. Solve missing addend problems (numbers to 10) mentally

• ### Where to next?

Uses count on from (think of addition) strategy to solve difference problems involving numbers to 20 eg understand 13 – 11 is the same as saying 11 + = 13
Use formal notation to record equations

• ### Purpose

Addition and subtraction are an important part of the skill set of a numerate person and are foundational skills for the other operations (multiplication and division) as well as for the larger body of mathematics.

• ### Building Addition and Subtraction skills:

The skill of adding and subtracting draws on all of the skills studied in the whole number section, and a failure to progress will generally indicate that one or more of these skills needs to be revisited.Understanding addition and subtraction begins with the realisation that the total of a collection changes when items are added or removed. The key skill at this stage is still counting, as students will initially use a ‘make all- count all’ strategy. That is, they will either add or remove a specified number of items from their collection, and then count the new collection starting at one to find the new total. Language is an important element at this level – linkng the idea of adding and removing items from a collection should be linked with words such as add, plus, take, minus and subtract and difference*.Once students are familiar enough with counting to ‘trust the count’ they will be able to add and subtract by counting on or back from the total. This is a very inefficient way of adding and subtracting however and as soon as students ‘trust the count’, they should start to explore patterns. These will be visual initially, through subitising and investigating the ‘part-part-whole’ nature of number using counters.Part-part-whole knowledge begins with exploring the structure of all the numbers to 10 – understanding that four is two and two or three and one for example. Part-part-whole knowledge can then be extended to larger numbers through an understanding of the base 10 and place value system ultimately leading to efficient mental methods of adding and subtracting.*Difference is an important idea as it leads to the understanding that add and subtract are just two different ways of looking at the same thing. Addition and subtraction should be taught as part of a single concept where possible.

#### Resources

Many of these activities are the same as those in the Part-Part-Whole section as the core concepts are identical. There is an added emphasis her on connecting these ideas to the language of addition and subtraction however.

### Activities and Assessments

Dot Doubles

Focus: Quickly determining the total of a collection presented so it can be visually perceived as two equal rows, or a “double’ number. Practicing and consolidating “doubles” number facts and using these to develop efficient addition strategies.

How: See Dot Doubles instruction sheet

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Dot Doubles card set

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Bees template

Doubles Memory

Focus: Building and consolidating “doubles” knowledge given numerals in the range to 12.

How: See Doubles Memory instruction sheet

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Doubles Memory card set 1

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Doubles Memory card set 2

Part-part whole board : Difference to 20

Focus: Solving “difference” or “missing addend” problems for totals to 20 without the use of counters or visual cues.

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Part-part-whole board

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Numeral Cards

Doubles Bingo

Focus: Building and consolidating “doubles” facts and applying these to develop efficient addition strategies.

How: See Doubles Bingo instructions

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Doubles Bingo game board

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Doubles Bingo numeral cards

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Doubles Bingo Spinner

Salute

Focus: For the Players: Solving “difference” or “missing addend” problems for totals to 20 without the use of counters or visual cues; For the Dealer: Finding the total of two numerals (each in the range to 10) by using doubles, near doubles and part-part-whole knowledge.

How: See Salute instructions

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Numeral cards to 10

Add / Subtract 5

Activity based indicators that students have achieved the target understandings

Download Assessment Points – Add / Subtract 5 sheet