Positive and Negative Numbers

Siegel, Lincoln R.             Cregier High School
6750 N. Ashland                Seely and Damen   
Chicago, Illinois              997-3690
262-58I7

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.)