Direct Variation Tables and Graphs

1. Cody rode his skateboard at a constant speed and then slowed down as he approached school. The story is shown on the graph.

a) How fast did Cody ride his skateboard when he rode at a constant speed?

b) How long did he ride at a constant speed?

c) How far did he ride at his constant speed?

d) What does the point (0.75, 0) mean?

Find the unit rate: .hours 4

30$

Direct Variation is:

A straight line

Goes thru (0,0) the origin

y = the same # times xy = 2xy = 3xy = ½ x

A table shows direct variation if:

is the same for every ordered pair

and

the table contains the point (0, 0)

x

y xy or

Determine whether or not the table models direct variation.

(0, 0) is a point in the table. For other points calculate . The ratio is for all points. Yes, the table models direct

variation.

x y y/x

0 0 --

1 2

2 4

3 6

4 8

1

2

1

2

2

4

1

2

3

6

1

2

4

8

x

y

1

2

Determine whether or not the table models direct variation.

(0, 0) is a point in the table. For other points calculate . The ratio is not the same for each ordered pair. No, this table does not model

direct variation.

x y y/x

0 0 --

1 1

2 2

3 4

4 5

1

1

1

1

2

2

3

4

4

5

x

y

A graph shows direct variation if it is a straight line that goes through the origin.

Determine if each graph models Direct Variation. Explain why or why not.

Graph A: Yes, the graph is a straight line through (0, 0). Graph B: No, the graph does not go through (0, 0). Graph C: No, the graph is not a straight line.

1. Determine whether or notthe table models direct variation.

2. What are the two things needed on any direct variation graph?

3. Draw a direct variation graph.

x y0 01 0.52 13 1.54 2

Is it more challenging for you to identify direct variation in a table or on a graph? Why?

Target: Recognize direct variation in tables and graphs.