Direct Variation

1
Direct Variation
2
Consider working at McDonalds
You get paid 8.00 per hour
3
Hours
Pay ()

• 1

8
X 8
2
16
X 8
3
X 8
24
10
80
X 8
In Direct Variation, one variable equals a fixed
multiple of the other.
4
Hours
Pay ()

• 1

8
X 8
2
16
X 8
3
X 8
24
10
80
X 8
This multiple is called the constant of
variation (k)
5
Hours
Pay ()

• 1

8
X 8
2
16
X 8
The formula
3
X 8
24
P
8
h
10
80
X 8
6
Pay vs Hours

• P

48
40
32
24
16
8
0
1 2 3 4 5 6
0
H
7
How much would you get paid for 3.5 hours?

• P 8 X 3.5
• 28

8

• P

48
40
32
28
24
16
8
0
3.5
1 2 3 4 5 6
0
H
9
Interpolation

• Using the graph to estimate values inside, or
  between graphed data.

10
How much would you get paid for 7 hours?

• P 8 X 7
• 56

11

• P

56
48
40
32
24
16
8
0
1 2 3 4 5 6
7
0
H
12
Extrapolation

• Using the graph to estimate values outside, or
  beyond graphed data.

13
Determine the constant of variation

• A jogger runs 50 km in 10 hours

k 50 / 10 5km/h
5.00 will buy a bag of 200 jelly beans
k 5 / 200 0.025 (or 2.5 cents each)
14

• Black McGraww Hill Ryerson
• Page 242
• 1-5, 7,8, 12, 14, 15 (homework)