Thursday, September 15, 2011

36 Club Subtraction tips

Subtraction is hard for a lot of children.  This method helped my children but there are kids that won't understand how to do it. It may seem too complicated. There was a girl in my son's 6th grade class last year who was having a really hard time passing off her subtraction. I told her this method and she immediately passed it off. I was amazed at how quickly she picked it up. So it will help some kids. It also depends on the child's attitude.  This girl really wanted to learn but I have worked with children who have convinced themselves they can't do it.  They won't even try.

This only works when the top number in the tens column is less than the bottom number in the tens column like this.

- 9

A lot of kids freak at this because they don't have eighteen fingers. So I tell them to subtract upside down. Take 8 from 9 and get 1. If the upside down answer is 1 then the answer to the problem is 9.

- 8

If the upside down answer is 2, then the answer is 8. (3 - 7 and 4 - 6.)

Go back to 18 - 9. If 18 were one more (19) then the answer to the problem would be 10. But 18 is one less than 19 so the answer is one less than 10. Notice the pairs always add up to ten.

This works because if the top number is 2 away from giving you the answer of 10, then the answer is 2 from 10 or 8.

If your child doesn't understand the upside down terminology, try the 1 from ten or 2 from ten. They can use this method for more complicated math, just don't let them forget that they still have to borrow!

I'd love to know if this helps anyone.

Addition Facts Here
Multiplication Facts
Division tips
Humdinger tips

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