ABSTRACT
This chapter explores how teachers can develop their capacity to ‘do it really quickly in their head.’ Developing teachers own mental methods in order to help them teach their pupils to calculate mentally can be challenging as teachers may not have been encouraged to do this when they were learning mathematics. Manipulatives like base-10 material, place value counters and Cuisenaire rods can be used to model calculations. Using these materials shows learners why the algorithms they are introduced to—to calculate using pencil and paper, such as column addition and subtraction—actually work. Counting is at the heart of calculating, and initially teachers will be working with their learners on counting objects and using language such as ‘more’ and ‘less’ to introduce them to ideas of addition and subtraction. The children will have developed their mental methods to include fractions and decimals and will be able to calculate percentage increases and decreases.
