Planning tool

Students:

• justify choices when partitioning and regrouping numbers to perform addition and subtraction
• mentally solve addition and subtraction problems using partitioning, rearranging and regrouping, and explain the strategy used
• use written recordings to clearly display the solution used
• apply strategies involving partitioning, rearranging and regrouping when solving worded problems.

Some students may:

• be able to identify place value parts and count orally to 100 and beyond but still think about two- and/or three-digit collections additively in terms of ones (for example, understand 468 as the sum of 400 ones, 60 ones and 8 ones). To address this, consolidate place value understanding by comparing and ordering two-digit numbers (for example, which is larger – 2 bundles of ten and 3 ones, or the number 41 shown on a number line), counting forward and backward by tens and ones, and by renaming (for example, 32 is 3 tens and 2 ones; it’s also 32 ones; and it can also be 2 tens and 12 ones).
• consider each digit in an addition problem as a separate number as opposed to representing a place value part. When using the vertical or column method, failing to recognise the place value of the digits leads to a lack of reasoning and precision. To address this, present addition problems horizontally and create habits of reasoning that draw on place value understanding through number talks and other activities that focus on mental computation and breaking numbers up into their place value parts.

• subtract the smaller digit, regardless of which appears first when using the vertical or column method, indicating a lack of reasoning and understanding of the operation being used. To address this, present subtraction problems horizontally and create habits of reasoning through number talks and other activities that invite mental computation strategies and involve thinking in terms of place value parts.

The Learning from home activities are designed to be used flexibly by teachers, parents and carers, as well as the students themselves. They can be used in a number of ways including to consolidate and extend learning done at school or for home schooling.

Learning intention

• We are learning how place value parts help solve addition and subtraction problems.

Why are we learning about this?

• We use addition and subtraction in everyday contexts.

What to do

Use two- and three-digit numbers every day.

1. Go on a number hunt. Look for, recognise and read the numbers around you, for example, numbers you notice around you on signs, calendars, speed signs and houses.
2. Use everyday opportunities to practise using mental addition and subtraction strategies, such as predicting the change you will get at the store.
3. Play ‘Guess my number’ or other games to put place value understanding into practice. Player 1 writes a two- or three-digit number on a piece of paper and the Player 2 asks ‘yes/no’ questions about it until they guess it. Example questions could be, ‘Is it larger than 500? Does it have an odd number in the hundreds place?’.

See mistakes as opportunities

• Know that mistakes are normal whenever we are learning or growing.
• When you get an incorrect answer, take the time to be curious about the mistake and see if you can learn from it. Which part of your strategy doesn’t quite make sense? How else could you approach the same problem?

Success criteria

I can:

• use the relationship between addition and subtraction to make some calculations
• solve addition problems mentally and verbally (for example, without pencil and paper) using place value parts
• solve subtraction problems mentally and verbally (without pencil and paper) using place value parts.