Friday, 5 December 2008

Teaching Subtraction

I have been teaching my middle son subtraction. Not just simple taking away, but 2 digits and 'borrowing' from the tens column. This follows teaching him addition with place value and it was quite a challenge getting him to begin adding the units and carry any extra tens. I pondered his dislike of this method for a while and came up with the idea of using money, not to bribe him, but for him to see in a concrete way what the place value meant and why he had to 'borrow'. I dug around in the parking change I keep in the car and in the children's pocket money purses until I had enough, then we sorted out pennies, ten-pence pieces and some pound coins. We got the required coins to make the amount given in the question, say 51p. Then I asked him to give me, say, 27p. Of course, it was obvious to him that he was stuck and couldn't do it, but he immediately took my suggestion that he trade one of his 10p pieces for 10 pennies. Then he could pay me what I was asking. This made perfect sense, he could grasp it, not only with his mind but with his fingers. We did a few and then I showed him how he could write down what he was doing. He was happy because it made sense, and wasn't nearly as hard as he had anticipated. I was happy because he was able to do it. The next day after a quick reminder he was off again.

However, I was then keen to get him to let go of the need for coins, to do it all on paper and we hit problems again. It is only in reflecting on this experience that I can see that he himself will naturally drop using the coins when they don't help any more. In other words, when he is so sure in himself of what to do, when he owns the knowledge, counting out the coins will become something he sees as a waste of time. He will find it quicker to write it down.

Why is it that, as 'teacher', I feel a need to push the children faster than they are ready to go (my daughter's reading is another example) instead of letting them learn and grow at the pace that is right for them? I think it is a natural instinct to want to challenge ourselves (think of all those multi-level computer games) and that we are the best judge of when we are ready to progress to the next level of difficulty. So, while my son has been learning about subtraction, I have been learning about letting him pace himself!


Anonymous said...

That's a great solution, and good insight into your own process. Sounds like they are all doing well.

Have you ever seen Great website for math. And there is a yahoo group that goes with it. Members use a lot of different styles and they are a great group to go to if you are having difficulties. Or even just for inspiration.

Gaynor said...

Thanks for the tip - at a first glance it looks like a website that could be really helpful- I will settle down with a cup of tea and have a good explore!