Q&A #4824

Teachers' Lounge Discussion: A different way to subtract than normally taught

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From: Ngaire

To: Teacher2Teacher Public Discussion
Date: 2009082322:43:02
Subject: Re: Re: A different way to subtract than normally taught.

Thankyou Frances! You are the first person I have "met", other than my brother and my Dad (who was our schoolteacher!) who uses the Compensation Method! I am Australian and we were taught this method in the 70s and 80s. EVERY maths curriculum I have looked at since (We homeschool our children) uses borrowing and it is soooooo clumsy. I do see that borrowing is an easier concept to grasp, but if the child can only get what we are doing when compensating, the method is then forever after soooo much speedier! We were taught thus: 34- 18 Add ten to the 4 in the units column so that we can take away 8: 14(units) - 8(units) = 6 (units). Then compensate for that "extra" addition of ten by taking away an extra ten in the tens column: 3 (tens) - 2 (tens) = 1 (ten). Answer: 16. We wrote a tiny little "1" up in the air just to the left of the 4 so that it looked like "14" (with the 1 tiny and up in the air) and a tiny "1" under and just to the right of the "1" in the tens column to remind us to take away an extra ten. So quick!!

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