Dividing Integers

1
Dividing Integers
2
Finding the Mean

• The mean is another word for the average.
• We find the mean by adding together all the
  relevant numbers and dividing by the number of
  numbers we added.
• Example the mean of 8, 5, 7, 6, and 4 is
• 8 5 7 6 4 30 6
• 5 5

3
What is the mean temperature?

• Add up all the temperatures and divide by 12
  (because there are 12 temperature readings)

Time Temp. (C)
Midnight -15
2 am -14
4 am -14
6 am -12
8 am -8
10 am -7
12 pm -5
2 pm -5
4 pm -6
6 pm -8
8 pm -11
10 pm -14
4

• 1) A cold front caused the temperature to drop
  8C in four hours.
• a) Use counters to show the mean temperature
  change per hour over the four hours.
• b) Share the counters into four equal
• groups.
• 1 2 3 4

5

• c) What is the result of (-8) (4)?
• -2
• d) What is the result of the following?
• (-20) (5) ii) (-36) (9)

(-8) (4)
6

• 2) In her weather project, Sarah reported a total
  temperature change of -8C and a mean hourly
  change of -2C. How many hourly temperature
  readings did Sarah make?
• Keep adding pairs of yellow
• counters until you have 8 yellow
  counters.
• Four pairs of counters
• means an answer of 4.
• (-8) (-2) 4
• What do these
• represent in Sarahs project?

7

• When you divide by a positive integer, you can
  think of sharing equally.
• (-12) (2) -6 (10) (2) 5
• When you divide integers with the same sign, you
  can think of repeated addition. (How many times
  do you need to add -2 to get -8?)
• (10) (2) 5 (-9) (-3) 3

8
Why can we not model (12) (-3) with integer
counters?
9
Relating Multiplication and Division

• 12
• 4 3
• This triangle can be used to illustrate the
• multiplication statement (4) x (3) 12,
• and the related division statements
• (12) (4) 3 and (12) (3) 4

10
Draw a triangle to represent (-4) x (-3) 12
11
Summary

• () ()
• () (-) -
• (-) () -
• (-) (-)

12
Summary

• () x ()
• () x (-) -
• (-) x () -
• (-) x (-)

13
Classwork

• Pages 232-233 1, 2, 3a, c, e, 4 8, 12, 16