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Efficient written methods for subtraction of £.p Y4/5/6

Discussion in 'Primary' started by elizabeth1972, Jan 14, 2012.

  1. I teach Y4/5/6 for maths, with abilities ranging from 2c to 5b.
    I'm planning for next week and I'm going round in circles with maths! I'm on the second week of A2, but we only have 2 weeks this half term for it.
    Last week, we looked at decimal numbers: place value, positioning on number lines, rounding and counting in decimal steps to create/continue sequences.
    This week, we really need to work on written methods for + and -
    On Monday, LA will use an expanded written column method to add pairs of three-digit numbers; MA will begin with expanded column method and then progress to the compact column method to add pairs of three-digit and four-digit numbers. HA will use the compact column method to add numbers with 1,2 and 3 decimal places.
    So far so good!
    On Tuesday, we really need to move on to subtraction using a written method. Only the HA are really very secure with this, so we'll do 1 day on whole numbers and then, if getting more secure, 1 day on £.p
    My question is, which written method is most appropriate as a starting point? Everybody (including me, if I'm perfectly honest) seems to find the counting up column method quite confusing, but the LA, especially the LA Y4s, won't get compact decomposition.
    I'm tearing my hair out here! Any ideas?
     
  2. Forgot to say, we don't have a school calculation policy!
     
  3. minnieminx

    minnieminx New commenter

    2c children are going to add pairs of three digit numbers? Really? My 2c children this week will be adding things like 56+16, with the second number less than 20 and the first such that the answer is still a 2 digit number. They will be using a numberline to do this.

    Same as subtraction, numberline for the level 2 and 3 children for sure. Good level 3s that you are pushing to level 4 this year move on to expanded columns (the subtraction makes more sense when you show it alongside a numberline to count up). Then level 4s beginning to use compact methods and level 5s using compact methods to do anything with any number in any situation!
     
  4. minnieminx

    minnieminx New commenter

    Be thankful! We do, but it is sooooooooooo stupid I, along with several other staff, ignore it entirely and pray no-one notices or cares!
     
  5. OK, sounds like I'm pitching too high on this. The majority of my class are Y5, L3s.
     
  6. marlin

    marlin Star commenter

    You could try looking at these documents to see if this helps you pitch your work. The first is for year 4, the second for year 5. There are documents like this for year 3 and 6 too:
    http://www.suffolkmaths.co.uk/pages/Primary/New%20Primary%20Framework/Year%204/Pitch%20&%20expectations%20Year%204.pdf
    http://www.suffolkmaths.co.uk/pages/Primary/New%20Primary%20Framework/Year%205/Pitch%20&%20expectations%20Year%205.pdf
     
  7. Thanks, Marlin. I do use the pitch and expectations documents, but they don't give you the expected calculation method.
    I'm looking at the info from the Strategies, and for Y4 A2, it says, "Refine and use efficient written methods to add and subtract two- and three-digit whole numbers and £.p but it still doesn't say by which method!
    I'm going to follow Minnie's advice and have the LA children using number lines, the MA using the expanded column method (possibly alongside ENLs to organise their thinking in terms of jumps) and try and push my highers on to the contracted method.
    I also think, after a bit of an unpicking of it all, that I'll only venture near decimals with my highers for now!
     
  8. CB123

    CB123 New commenter

    Although the objective may say adding / subtration of £ p, personally I would not go near this until your children are secure with adding / subtracting whole numbers. Have you got a break down of level descriptors for each level as this may be more useful than just going from the objective.
    For subtraction I find using a number line by finding the difference (eg 53 - 27, How much do I add to 27 to get to 53?)is the most efficient initially as it makes them understand more what they are doing - going into the columns too quickly can often result in children learning a method but not understanding fully what it means and thus making mistake as the calculations get trickier
     
  9. minnieminx

    minnieminx New commenter

    Click on the 'progression through sublevels thing' in this to help you pitch the work. This document has become my maths bible this year when thinking, for the first time ever, about level 1 and 2!

    https://www.westsussex.gov.uk/learning/west_sussex_grid_for_learning/curriculum/mathematics/primary_mathematics/assessment/progression_through_sublevels.aspx
     
  10. Great document, Minnie. Thank you, it looks just the thing!
    I'm having a particularly bad day planning today... I've been at it solidly since just gone 12, and seem to have got nowhere. Hubby has just wandered past and asked who I am!
    The most annoying thing is that I've got practically nowhere, and envisage another day chained to the laptop tomorrow. Aaarrggghhhh.
     
  11. minnieminx

    minnieminx New commenter

    LOL You need a student teacher! My maths is all planned for next week and exciting and fun and everything.

    Naturally I'm planning the literacy which is just a sketchy outline!
     
  12. Give me literacy any day... interactive, differentiated in a gazillion different ways, lots of speaking and listening and drama: lovely! I can plan my whole week in an hour!
     

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