# Count on or count back for subtraction?

Discussion in 'Primary' started by madmusician, Feb 28, 2016.

1. ### madmusicianNew commenter

Hi
Currently in my school, the policy has been we count on to subtract on a number line in years 1 and 2.

In my previous school, we counted back.

I prefer counting back but wondered what others do. I teach year 2.

Many thanks

MM

2. ### Lara mfl 05Star commenter

Both are equally valid of course.

Personally I preferred counting back, as the 'technique' was easily adapted to 'counting back in groups' for division. It does presuppose that one knows the answer of course.
However when it comes to answering question with missing values like 7 + ? = 10 counting on could come into its own and the 'counting back' method used as a check.

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3. ### GordonWrightNew commenter

Counting on every time for me.
They make more errors counting backwards.
I tell those who struggle with subtraction that they never actually need to subtract. As long as they can add (count on), they can do 'subtraction' sums. It helps some of those whose mind is 'blocked' against succeeding with subtraction.
(I'm KS2 by the way.)

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4. ### TEA2111Established commenter

I think that chd in Yr 2 should be taught to do both as it is a method in which to get chd to practise counting backwards and forwards. It is very important though, that they are taught to 'subtract by adding on' as I still have yr4s who do simple subtraction sums by counting backwards.

5. ### madmusicianNew commenter

Thanks everyone. I've taught juniors too and have always had some who have struggled which ever way. We have taught counting on last term and earlier this term but I find some get confused and add rather than subtract when using the counting on method. We will see how it goes this week.

6. ### carriecat10Established commenter Community helper

I agree that children should have experience of a range of strategies so they are better able to decide which is the most efficient. For example 83 - 75 it makes sense to count on as the numbers are fairly close together. However 83 - 7 it makes sense to take away or count back.

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7. ### caterpillartobutterflyStar commenter

Both methods for me too.
If the number being subtracted is small, count back. Otherwise count on.

8. ### onmykneesEstablished commenter

I think children need to be aware that subtraction means that the number is getting smaller. The other method is called find the difference which is slightly different. They need to have understand both concepts and when they are most efficiently used. I think it's very naive to teach only one way.

9. ### caterpillartobutterflyStar commenter

They really don't! Subtraction does not mean that at all and they have to unlearn it when they reach upper KS2 and use negative numbers.