# Singapore 1.A math - lost my teachers book

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I have a student doing Singapore math. We're in 1.A and I've misplaced my teachers manual.

How do they explain subtraction including borrowing - questions like 17-9?

I know they have their own way of explaining things, and would like to maintain their processes.

17 - 9

1. (10 + 7) - 9

2a. 10-9 = 1

2b. 1+7= 8

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1-A certainly does cover 17 - 9; we are doing it now!

Another approach they have for 17 - 9 is splitting up the 9 into 7 and 2, so you can take the 7 away from 17, leaving you with 10-2.

I prefer the 7+1 method, because there are two ways to teach it beyond number bonds. First, the number line method: the distance from 17 to 9 is the distance from 17 to 10 plus the distance from 10 to 9. This will help a lot with mental math.

The other thing is that it's easy to use money: I call it "shiny dime and grimy pennies". For 19 - 7, you don't have to get rid of your shiny dime, as you have enough pennies: 19 - 7 = (10+9) - 7 = 10 + (9-7) etc. For 17 - 9, your seven pennies aren't enough, so you've gotta lose your shiny dime, for which you'll get one penny in change.

For drills, we xerox (do folks still use that verb?) the Mental Math exercises and have her demonstrate number bonds using both methods.

The HIG has other great games that we regularly incorporate. I consider it essential for 1A if you can afford it.

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Thanks for all your help. That's what i remembered from my first student but my newest student is having problems with the concept.

What is the HIG?

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HIG = Home Instructor's Guide

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Are you sure? I don't see that absolutely anywhere in 1A. Could you be talking about 2A?

Maybe you're using a different edition. My standards ed. has problems like that in the unit on "Numbers to 20".

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The SE 1A definitely does have a great number of equations of the sort mentioned.

Bill

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