Children understand subtraction best when it is taught alongside addition. Furthermore learning is better if it is given a context. For younger children a scenario such as ‘I had five oranges and we ate two. How many do we have left?’ leading to older children’s understanding of ‘I had two fifty pence coins and spent 25p at the shop. How much change did I receive?’ gives children a real reason for learning subtraction and is more engaging then an abstract calculation on its own. Calculation methods are taught and learnt to be used to solve problems such as these.
Many of the written methods learnt at school now differ from those parents and teachers learnt themselves. We teach them because they help understand ‘place value’ (for example what the 4 in 245 means as opposed to 425) and often link with what we do in our heads to solve a calculation.
When children first subtract they need to use ‘concrete‘ resources such as cubes and need to physically ‘take away‘ a given number to find the answer. (Slides 1 and 2)
Children then start creating their own informal ways of recording this. (Slides 3 and 4)
As children experience ‘100 squares’ and ‘number lines’ and are able to count to higher numbers they use these to support their calculating skills. Children learn to count backwards, ‘one less‘ (and later ‘ten less‘), and use given ‘number lines‘ to solve subtraction. (Slides 5 and 6)