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Good way to teach subtraction as the difference - year 1

Discussion in 'Primary' started by pocoyo, Jun 4, 2011.

  1. I find this a very tricky aspect of maths to teach as i think it's difficult for children to grasp doing addition and subtraction in one go. I was wondering whether anyone has a way of teaching this in a very simple way which explains it very easily?
    Any games or interactive programmes that explain this well would be great also.
    Thank you so much in advance xxx
     
  2. Try getting them to 'add on'....how many cubes do I add on to 3 cubes to get 7 cubes.
    They won't even know they're subracting until you tell them.
    Good luck
     
  3. Towers of bricks so they can see it visually.
    Learn words more and fewer - what is the difference - which tower has more / fewer. Numicon if you have it another great visual.
    For your more able children, this interactive acitivity goes down well with my class - count on from the smaller number to find the difference/ count back from the larger number to find the difference OR - can you do a subtraction to find the answer.
    http://nlvm.usu.edu/en/nav/frames_asid_326_g_1_t_1.html?from=grade_g_1.html
    I will put some ppts that I use in resources.


     
  4. flapfish

    flapfish New commenter

    This is tricky. I found the children got it if you showed 2 numbers e.g.5 and 8 ans two rows of circles one on top of the other and asked 'what would I have to do to 5 to make it into 8? 'They could all see that you would add 3. You could then model how this could be worked out by counting on, adding or using knowledge of number bonds. If you then say 'what would I have to do to 8 to make it into 5?' They can see that you would take 3 off and you can then model how you might work that out by counting back or taking away. Drawing rows of dots is very visual for small numbers. I have used dominoes (working out the difference between the number of dots on each side), stones, counters... For the less able just seeing the difference is doable and for the more able, making the jump to mathematical ways of findong the difference can still be supported visually if necessary. Hope this makes sense.
     
  5. Thank you for your replies. In the APP level 2 it requires children to be able to write sentences such as 8 + 5 = 13
    13 - 5 = 8

    So they are basically trying to get back to the first number. They have to be able to write the subtraction fact to the addition. Would you still use cubes for something like this? How would you set up the main activities for this??

    Thank you xxx
     
  6. thepinkrachael

    thepinkrachael New commenter

    My class find this so hard! Cubes as previously said. We have also made playdough bugs with a partner and lined them up: who has more/fewer, how can we make them the same/how many more/fewer/what's the difference and recording as addition only for lower ab., using lines of pennies and dots too.
    We have also used a large number track, two children throw a beanbag each along the track. They jump to the lower number together then count 'how many jumps' to their next number and again record as appropriate for ability. You could do this in reverse afterwards to help them see it as a subtraction as well (for example throw to 7 and 12, jump to 7, count on to 12, record as 7+5=12), now they are both on 12, jump back to 7 and count how many again, talk about the fact it si the same and record it under the first sum so they can see that the numbers 'change palces' but stay the same. hope that makes sense.
    We have used a higher or lower style card game, where children have pile of cards each. One child turns their card and the others guess whether the next will be higher or lower, it's turned over (is it higher/lower, by how much - whats the difference?). they count on (in heads, with number lines, as app.) to find difference and first one to 'buzz' gets to choose who to play against and carry on the game. We always check to see if that person is right by working it out together, so again you could do this both ways, count on to find the difference and record as an addition, count back again and record it as subtraction.
    Just a couple of ideas anyway!
     
  7. mystery10

    mystery10 Occasional commenter

    All these lovely ideas above help. With my own children at home, and children I have volunteered with, I find that a medium sized 100 square works very well too. It's good to have one of an appropriate size which they can hop along with their finger and see that it's the same number of hops to go from 12 to 18 as it is to go from 18 to 12 - loads of examples like this and they can see for themselves that 12 + 6 = 18, and 18 - 6 = 12 and that they can find the difference of 6 either by counting up or counting down. The individual number square that the school printed off ********** in year 1 was way too small for even little fingers.
    There must be an interactive whiteboard tool for this too?
    They can also do it on their fingers - put 12 in your head, count on up to 18 sticking up a finger each time - you get 6 fingers. Or count backwards - put 18 in your head and then count backwards sticking up a finger each time down to 12 - again you have 6 fingers sticking up.
    Lots of being able to count backwards and forwards stopping and starting at specific numbers is a precursor.
    All the other methods people have suggested are better and more interesting for teaching the concept, but for regular practice the number square and finger methods are good as they don't require special equipment to be available for every child every time you want to do some quickfire practice.
    Paper plates with biscuits or sweets or plastic teddies are good too.
    e.g. put 3 teddies on a plate. How many more do I need to put on the plate if I want 7 teddies in total on the plate - count on 4, 5, 6, 7 while adding teddies. How many more teddies have I put on the plate? 4. So 3 + 4 = 7 (can make up some interesting stories rather than just the plain question)
    How many do I need to take off so that I only have 3 on the plate - count back 6, 5, 4, 3, while taking off the teddies. How many teddies did I take off? 4 . so 7 - 4 = 3
    Children who like to draw out problems can quickly represent the teddies on the plates as dots in a circle and work things out visually as well as with the number sentences. The plates and teddies can be readily available for those who like to use concrete methods or check their working with concrete methods.
     
  8. Be careful using 100 squares - they can be confusing as the children count over the tens boundary- I find a tape measure with cm to 100 works quite well, they can put their fingers on both numbers and see and count on the difference.
     

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