Download Lessons 1_7-1_9 direct variation _ constant rate of change

• Rate of change: is a rate that describes how one quantity changes in
relation to another
• Constant Rate of Change: is change in the y over a change in the x.
• Direct Variation: when 2 variables quantities have a constant ratio
• Constant of Variation: is the constant ratio
• Constant of proportionality: is also the constant ratio
• Examples
Find the unit rate to determine the constant rate of change.
Number
Money ($)
5
10
40
Time
30
Distance
290
80
60
580
15
120
20
160
90
120
870
1160
• Direct Variation is when the ratio of y to x is a constant, k. We say y varies
directly with x.
• Symbols: y/x=k or y=kx
• Examples (skip 3 lines between question)
1. The equation y=10x represents the amount of money Julio
earns for x hours of work. Identify the constant of
proportionality.
2. Pizzas cost $8 each plus a delivery charge of $3.00. Show the
cost of 1,2,3 & 4 pizzas. Is it a direct variation?
Time, $, y
x
3. Determine whether the linear relationship is a direct
variation.
1
12
If so, state the constant of proportionality.
2
3
4
24
36
48