Teacher2Teacher Q&A #522

Teachers' Lounge Discussion: Teaching subtraction

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From: Diane

To: Teacher2Teacher Public Discussion
Date: 2006080409:27:37
Subject: Re: teaching subtraction

How to teach a year 2 child to do borrowing rather begs the question, why? At this age children are far better occupied developing intuitive strategies based on a full understanding of subtraction. It is not just take-away, but also "difference". This understanding allows children to use the relationship between addition and subtraction to solve problems. The easiest way to solve subtractions involving zeros is to "build-up" to the tens or hundreds. For example 300 - 189. From 189 you need to add 1 to go to 190. From 190 you need to add 10 to go to 200. From 200 you need to add 100 to go to 300. The difference between 300 and 189 is therefore 1 + 10 + 100 = 111 That said, if you have to do borrowing I have a way, if the children understand place value. Consider again 300 - 189. Subtracting the units first we see 0 - 9, which can't be done. When you go to the next digit it is also 0...no help. The three hundreds can be thought of as 30 tens. You can take one of these tens leaving 29 tens. Cross out the 30 and replace it with 29. Give the ten to the units. Then 10 - 9 = 1, 9 - 8 = 1, 2 - 1 = 1. Again 211.

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