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Date: 5/29/96 at 16:42:52
From: Jason Johnson

Hello Dr.Math...

I am currently in grade 8 and I am doing adding and subtracting
me?

Jason Johnson
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Date: 6/25/96 at 15:29:39
From: Doctor Robert
Subject: Re: Adding and subtracting integers

Dear Jason,

Probably the easiest way to 'visualize' addition and subtraction of
integers is to use a number line.  I am sure that you are familiar
with a number line.  If you need to add two integers you go to the
point on the number line which represents the first number and then
you count to the right the number of dots equal to the second number.

It doesn't matter which number of your sum you call the first number
and which you call the second number.  For example, suppose that you
have to add 12 + 5.  Go to 12 on the number line and then count 5 dots
to the right.  What number did you land on?  17!  And 17 is the sum of
12 and 5.  You could have gone to 5 and then counted 12 dots to the
right.  You would still land on the number 17.

For subtraction, you must go to the first number and then move LEFT
the number of dots corresponding to the second number.  For example,
17 - 9.  Go to 17 and then move LEFT 9 dots.  You wind up on 8 which

I hope that this helps.  It gets a little bit more complicated when
you have signed numbers to add and subtract.

-Doctor Robert,  The Math Forum
Check out our web site!  http://mathforum.org/dr.math/
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