Adding and Subtracting IntegersDate: 12/31/97 at 20:07:08 From: Tracey Subject: How to add and subtract integers I need help on how to add and subtract integers. An example of a problem would be 12 + (-4) = ?. What I do is just add the problem, but the answer turns out to be 16. Then I would check it on my calculator and the answers is 8. I need help on the steps, and if you could explain how you did each step it would be very helpful. Thank you. Date: 01/09/98 at 14:33:21 From: Doctor Sonya Subject: Re: How to add and subtract integers Tracey, I can understand your frustrations in dealing with positive and negative numbers. It is a very difficult topic, but I know that you will get it with practice. When I think of adding and subtracting negative numbers, I always imagine a number line, like this: <---------------0--------------> where each little dash stands for a number. The negative numbers are on the left of 0 and the positive ones are on the right. If I want to find 2 on the number line, I just go 2 spaces to the right. If I want to find -3, I go 3 spaces to the left. When you want to add two numbers together, think about moving on the number line. For example, if I wanted to find the answer to: 3 + 5 = ? I would first move three spaces, and them move 5 more spaces. This would put me 8 spaces over, and the answer to 3 + 5 is 8: <---------------0---3-----8------> 3 + 5 The same principle works with negative numbers, except that you move to the left instead of to the right. Say you have the question: (-3) + (-2) = ? To find the answer I'm going to move three spaces to the left, and then 2 more spaces to the left: <-----------(-5)---(-2)--0----------------> -3 + -2 If the two numbers are of different signs, you just have to move different directions along the number line. Let's say I have: (-3) + 4 = ? Now, the -3 means that you move three spaces to the left, and the 4 means that you move 4 spaces to the right. Where is this going to put you on the number line? <--(-5)-(-4)-(-3)-(-2)-(-1)-0-1-2-3-4-5-6-7-8-9-10-11-12-> Still thinking... . . . Hmmmmmm. . . . No answer yet... You say that the answer is 1? Right! Good job. Here are some more examples for you to practice with. 2 + 4 = (-3) + 8 = 3 + (-5) = (-5) + (-6) = 8 + (-5) = 5 + 2 = (-4) + (-3) = Write us back if you have more questions. -Doctor Sonya, The Math Forum Check out our web site! http://mathforum.org/dr.math/ |
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