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					                         The A to Z’s of Math Activities
                           N is for Negative Number
Background
       A negative number is a number with a value less than zero. It is
usually written with a minus sign (-) in front of it. Numbers greater than
zero are positive numbers. They can be written with a plus sign (+). Any
number that is not preceded by a sign is a positive number.
       In mathematical terms a minus sign (-) can also mean subtract; while
a plus sign (+) can refer to addition.
       Historically, negative numbers were first written about during China’s
Han Dynasty (202 BC to 220 AD).

Materials                                Vocabulary
Activity 1                               Minus represented by –
 Circle Patterns                         can mean (1) negative number or (2)
 Red and green crayons                   take away, subtract
 Scissors                                Negative number a number less than
Activity 3                               zero
 Graph paper                             Plus represented by +
 Ruler                                   Can mean (1) positive number or (2)
                                         keep, addition
                                         Positive number a number greater
                                         than zero
                                         Zero indicates no value

Activity 1
SET UP        circle pattern sheet, red and green crayons, scissors
              Color half of the circles red and half of the circle green, cut out
the circles

Circle Patterns




OOOOOO
OOOOOO
                       The A to Z’s of Math Activities
                         N is for Negative Number




OOOOOO
OOOOOO
Activity 1   Combine Positive and Negative Numbers
                               Write problem on the white board
                               Example:    -3 + (+2)

             STEP ONE          Use circles to represent the numbers
                               Red circles represent negative numbers
                               Green circle represent positive numbers
                               Set out 3 red and 3 green circles, next to each
other
                               Set out 2 red circles and 2 green circles, next
to each other




             STEP TWO          Begin with -3
                               Remove the 3 green/positive circles
           The A to Z’s of Math Activities
             N is for Negative Number




STEP THREE         What is the problem asking you to do?
                   Answer: add or keep


STEP FOUR Keep the +2
                Remove the 2 red/negative circles




STEP FIVE          Partner up, remove pairs of one red and one
                   green circle until only one color remains




STEP SIX           What is the answer?
                   Answer: There is one red remaining so the answer is -
                   1
                   (If there were none left, the answer would be zero)
                       The A to Z’s of Math Activities
                         N is for Negative Number




Try it again
                   Write problem on the white board
                               Example:    -4 - (-1)

               STEP ONE        Use circles to represent the numbers
                               Red circles represent negative numbers
                               Green circle represent positive numbers
                               Set out 4 red and 4 green circles, next to each
other
                               Set out 1 red circle and 1 green circle, next to
each other




               STEP TWO        Begin with -4
                               Remove the 4 green/positive circles




               STEP THREE      What is the problem asking you to do?
                               Answer: subtract or take away
                        The A to Z’s of Math Activities
                          N is for Negative Number
             STEP FOUR Take away the -1
                             Remove the 1 red/negative circle




             STEP FIVE          Partner up, remove pairs of one red and one
                                green circle until only one color remains




             STEP SIX           What is the answer?
                                Answer: There are three red remaining so the answer
                                is -3



Additional problems:
+3 + (-2) = +1    -3 + (-2) = -5       +3 – (+2) = +1
+4 – (-1) = +5    +4 + (+1) = +5       -4 – (-1) = -3
+2 + (+2) = + 4   -2 + (+2) = 0        +2 – (-2) = +4




Activity 2   Think about it
             Have students work in small groups
             Review problems and answers on the white board
             Ask students what they observe
                         The A to Z’s of Math Activities
                           N is for Negative Number
             Possible answer:
             A negative negative equals a positive (Comparative to a double negative
      when you speak)
             A negative sign telling you what to do will change the sign of the next
number




Activity 3   Optical Illusion
SET UP       Graph paper, ruler, pencil, pen

      STEP ONE             Use the ruler to draw two intersecting lines in pen
                           Draw the lines in the middle of the graph paper

       STEP TWO            Use a pencil; mark the space where the lines
intersect 0

     STEP THREE         Use a pencil; begin at the 0 and move right,
number each line +1to +11
                        These numbers represent values MORE than zero

       STEP FOUR Use a pencil; begin at the 0 and move left, number each
line -1 to -11
                       These numbers represent values LESS than zero

       STEP FIVE           Use a pencil; begin at the 0 and move up, number
each line +1to +11
                           These numbers represent values MORE than zero

     STEP SIX             Use a pencil; begin at the 0 and move down,
number each line -1 to -11
                          These numbers represent values LESS than zero
                  The A to Z’s of Math Activities
                    N is for Negative Number

     STEP SEVEN     Use the ruler and the pen to connect pairs of
numbers:
                    Note:
                    the first number represents the numbers on the left
                    to right line
                    the second number represents the numbers on the
                    up and down line
                           (left to right line, up and down line)

                    (+1, +11) (+2, +10) (+3, +9) (+4, +8) (+5, +7) (+6,
                    +6) (+7, +5) (+8, +4)
                    (+9, +3) (+10, +2) (+11, +1)

                    (-1, +11) (-2, +10) (-3, +9) (-4, +8) (-5, +7) (-6, +6)
                    (-7, +5) (-8, +4)
                    (-9, +3) (-10, +2) (-11, +1)

                    (+1, -11) (+2, -10) (+3, -9) (+4, -8) (+5, -7) (+6, -6)
                    (+7, -5) (+8, -4)
                    (+9, -3) (+10, -2) (+11, -1)

                    (-1, -11) (-2, -10) (-3, -9) (-4, -8) (-5, -7) (-6, -6) (-7,
                    -5) (-8, -4)
                    (-9, -3) (-10, -2) (-11, -1)




    STEP EIGHT      Erase the pencil marks
                           The A to Z’s of Math Activities
                             N is for Negative Number

      Why do the lines appear curved?
      Answer: It’s an optical illusion



Extension
Find out what other discoveries were made by ancient China.
Use Activity 3 as an introduction to Cartesian plane and coordinate points.
What is an optical illusion? Find one to share with the class.

				
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