**Positive and Negative Numbers**

Siegel, Lincoln R. Cregier High School

Seely and Damen

997-3690

**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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