Positive and Negative Numbers

Siegel, Lincoln R. Cregier High School
Seely and Damen

Objectives: Students should be able (after concrete examples are shown) to realize that zero is not the lowest number used in mathematics or real life, that there are NEGATIVE numbers and how to use them. Materials Needed: Acetate paper Pointer Screen Light (for screen) Various colored crayons Strategy: By using the number line (vertically) and the "team" method to introduce adding and theory AND a practical method of performing subtraction involving any possibility (or combination), it is hoped that students will feel at ease with negative numbers even though they will continue to prefer positive numbers and concepts in their daily life. (The number line method is familiar to math teachers; the "team" method is merely a grouping of all positive numbers together under a plus sign and doing the same to the negative numbers under a minus sign, determining which sign has the bigger total, and applying this sign to the difference of the two "teams." Subtraction will involve the teacher emphasizing it is NEGATIVE adding, using positive and negative minuends and subtrahends, demonstrating the difficulty of finding the exact differences in many cases. As a result the teacher will by example demonstrate that subtracting is negative adding by inquiring of the class if they do not see that giving a student a negative sum of money is not the same as taking that very sum away. The method of changing any subtrahend's sign to the opposite sign, and treating the result as an adding problem will give the correct answer to the subtraction problem. It will be mentioned, also, that the changing of signs should occur on the side to allow the teacher to see the original problem. Three of the four possible combinations will be done in this manner. Finally the method will be shown to work on two POSITIVE numbers, thereby recalling a simple second grade problem to reassure students that changing the method of subtraction does not violate what they have already learned.)
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