This week we have been revising our subtraction skills as this is one of the areas most children are finding quite difficult to master. Subtraction is always tricky, doing things backwards is always harder, its not as well rehearsed as counting forwards or adding on. Have you ever tried to say a nursery rhyme backwards? It's a bit like this for children when they try to count backwards. So to make it easier there are several approaches you can take, you might like to try these at home:1. Don't count backwards! Find the difference between two numbers by counting forwards, especially if they are close together. For example for 56-44. Start at 44 and count on up to 56 to find the difference.
2. Use your knowledge of 10s and 1s. See if you can practice subtracting multiples of 10, for example: 34-10, 65-20, 44-20, etc. Practice counting back small amounts: 44-2, 65-3, 42-5. Using a hundred square like the one in this blog may help with this. To subtract a 10, just jump up a square, to subtract a 1 move left.
3. Know those number bonds. When subtracting over 10s boundaries (when your subtraction takes you into the previous 10, for example you know 35-7 is going to take you into the 20s) it is essential to know your number bonds to work this out quickly.
We know that 35-5 takes us back to 30, but we wanted 35-7 so we also have to know that if we have already subtracted 5 that we have 2 more left to subtract. Furthermore we also need to know that if we take 2 from 30 we are going to land on 28. In class we use a hundred string to help. I've included one in this blog.4. Finally, we have started to learn formal methods for subtraction where you lay out the subtraction with one number on top of another. Some children are beginning to understand how to use a ten to exchange for 1s to enable them to take away.
Above all it is important that the children have lots of practical experience of subtraction, so try it at home with whatever is to hand - pasta, seeds, toys, etc. It will all help!
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