This displays the Getting started on page 75 of the Student Resource Book.

• Teachers could use this to give students opportunity to investigate and explain the relationship between two parts of a double using materials.  Students might identify the symmetry between the two parts that make the whole or they could investigate what happens when even or odd numbers are halved or doubled.  This encourages students to reason, make conjectures and generalise in ways that might be particularly helpful in this chapter and are essential for algebraic thinking.

This two-page document gives an example of using doubles to add and an example of using doubles subtract two-digit numbers.

• Doubling two-digit numbers requires students to combine their number knowledge with a strategy to find a near double. The first slide demonstrates how students can combine their knowledge of basic fact doubles and place value partitioning to work out the double. Because the example is a near-double, students also need to think about whether the extra quantity (usually one or two) needs to be added or taken away from the total.
• Halving double digit numbers can be difficult especially if students lose sight of place value. For example, students may need to be reminded that the digit one in the tens place is worth 10 and this can be easily halved.
• Using place value materials, for example, Unifix towers or ice block stick bundles, alongside these sheets will help students make sense of doubling and halving if they are having difficulty.

This displays a sheet where students are asked to write down the sums of numbers that make a tens number or 100 and then calculate the total.

• Teachers could use the first example and hint which aligns to the first row to clarify the activity for students and discuss strategies for adding a list of numbers, such as scanning along for numbers in the ones or tens place that add to ten, jotting down the sum and crossing off numbers that are not needed.
• Students could then work through the remaining examples independently, with a buddy, or discuss them as a class.

This displays a sheet where students are asked to find numbers in a row that add or subtract to 0 and write down an equation using the numbers that are left.

• Teachers could use the example to clarify the activity for students and discuss strategies for adding a list of numbers, such as scanning along the equation for the number being subtracted and facts that equal that number, crossing off numbers that are not needed etc.
• Students could then work through the remaining examples independently, with a buddy, or class discussion.