How much time should we spend on subtraction?
Last week a temporary contract teacher asked me to look at the scope and sequence she had been left for the Year 1 class she was teaching for 2 terms.
The previous term had been all about number and addition. She was about to launch into subtraction but sensed that the 2 weeks allotted would be insufficient to do the job with deep understanding. She was absolutely right of course.
We know that even adults find subtraction harder than addition and division harder than multiplication.
We also know that most adults do subtraction by addition most of the time, that is they use a count on or count up strategy rather than a count back strategy. If the numbers are large or if they have been over taught the traditional pencil and paper method, they cannot apply efficient mental computation strategies and rely on cumbersome digit-based strategies.
A simple example of this occurs when I ask a roomful of a adults how they would subtract 76 from 152. Think about how you would do it before reading on.
Back to the question:
“How much time should be allotted to subtraction?”
The answer is a lot more than 2 weeks.
I have just finished writing our Early Subtraction series and am surprised at just how much students need to know and understand in order to even carry out small digit subtractions fluently and meaningfully.
Working with students in classrooms I often find that many students:
- do not have the concept of take away,
- are not fluent with less than, number before,
- cannot count back from any starting number,
- have insufficient experiences with number splitting and finger gnosis,
- have difficulty connecting addition with subtraction and known facts.
Clearly even this very rudimentary list of ‘crunch points’ will take more than 2 weeks to address. Of course, it begs other issues too, such as whether addition and subtraction should actually be taught together.
If you are interested in giving students a firm foundation in subtraction the following Natural Maths products are available to help. Early Subtraction – a set of teaching resources in 6 individual modules or available as a complete package Subtraction Mat 1 and Subtraction Mat 2.
Thanks for reading!