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Count on or count back for subtraction?

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

  1. madmusician

    madmusician New 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 05

    Lara mfl 05 Star 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.
     
    madmusician likes this.
  3. GordonWright

    GordonWright New 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.)
     
    TEA2111 and Lara mfl 05 like this.
  4. TEA2111

    TEA2111 Established 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. madmusician

    madmusician New 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. carriecat10

    carriecat10 Established 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.
     
    TEA2111 and madmusician like this.
  7. caterpillartobutterfly

    caterpillartobutterfly Star commenter

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

    onmyknees Established 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. caterpillartobutterfly

    caterpillartobutterfly Star 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.
     

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