1. Direct Variation
The graph of a direct variation is always a line that passes through the origin.

2. Direct Variation
When two variables are related in such a way that the ratio of their values always remains the same, the two variables are said to be in direct variation.

3. Definition
A direct variation can be described by an equation in this form:
The letter k represents the constant of variation.
You say that y varies directly with x.

4. If y varies directly as x and y = 8 when x = 12, find k and write an equation that expresses this variation.

5. If y varies directly as x and y = 24 when x = 16, find y when x = 12.

6. To Do….in groups of 3/4
In both inches and centimeters, find the length of
One shoe in your group.
The smallest assignment book in your group.
The youngest person’s index finger.
The oldest person’s wrist.
The other person’s wrist to elbow.
Make a scatter plot of these data. Decide as a class which unit to put on the x-axis.
Find a line of fit.
Identify and interpret the meaning of the slope.
Identify and interpret the meaning of the y-intercept.
Is this a direct variation?