Number & Algebra

Chapter 1 | Adding and subtracting using tens numbers

(Getting started before page 61 to revise the concept of tens numbers.)

For each number, students might identify the previous ten and the next ten, and link this to addition (moving to the right on the number line) and subtraction (moving to the left on the number line).
Discuss which facts are helpful for making tens numbers and encourage students to practise facts that make ten if they cannot easily recall them.

(Further discussion following the teaching section page 64 for various ways of partitioning to a tens number to solve subtraction problems.)

Students could use the materials shown or other materials (such as Unifix cubes), to explain to a partner how Max solved the equation using a tens number. It is important that students find a way to show or record their thinking and the solution to each
You may need to draw students’ attention to the way this strategy first subtracts the number in the ones place (to get to a tens number), and then if necessary breaks a ten to subtract the rest of the number. This is a good opportunity to emphasise the usefulness of knowing facts to 10.

(After the teaching section to support the discussion on page 67 for adding in parts through a tens number to solve an addition problem.)

Partitioning for addition is often more problematic for students than subtraction, as the ’best fact’ to use is not so obvious, especially for students who do not know the facts to 10.
It is important that students find a way to record their strategy and check that they have actually answered the question.

(To support the discussion on page 67 for adding by making a tens number.)

A good knowledge of basic facts is particularly important for this strategy. Students who understand the strategy but have difficulty recalling the facts could make their own list of facts that make ten. This helps them decide which fact will be most useful.