Download 9-7 Write and Solve Direct Variation Functions Wkst

Pre-Algebra
Name ___________________
Date ___________ Period ___
Unit 9 –Solving Equations
9-7
Writing Direct Variation Equations
Determine whether the set of numbers in each table is models a Direct Variation.
1.
Blue Paint (quarts)
1
2
3
4
Yellow Paint
(quarts)
5
6
7
8
Junk E-mails
10
20
30
40
Total E-mails
15
30
45
60
3.
2.
Ice Tea Mix
(cups)
1
2
3
4
Sugar (cups)
2
4
6
8
Jars
3
9
12
15
Jelly Beans
18
36
54
72
4.
Determine whether each graph models a Direct Variation.
5.
6.
7
6
5
5
4
4
3
3
2
2
1
1
1
7.
7
6
2
3
4
5
6
7
8
8.
3
2
1
1
2
3
4
5
6
7
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
3
2
1
1
8
-1
-1
-2
-2
-3
-3
Step 1: Write the direct variation equation,
y  k x.
Step 2: Find the k value by either plugging in the given x and y or by using the formula
y
k 0 .
x0
Step 3: Re-write the equation from Step 1 by using the k value that you found in Step 2.
Step 4: Once you have your equation, solve each question by substituting the x or y value into
the equation and solve for the other variable.
9. Suppose y varies directly as x , and y = 10 when x = 2 .
a) Find the value of k .
b) Find the slope of the line.
c) Write the direct variation equation.
d) Graph the equation.
e) Find y when x = 3 .
f) Find x when y = 60 .
10.
Suppose y varies directly as x , and y = 12 when x = 4 .
a) Find the value of k .
b) Find the slope of the line.
c) Write the direct variation equation.
d) Graph the equation.
e) Find y when x = 7 .
f) Find x when y = -18 .
11. Suppose y varies directly as x , and y = 4 when x = 8 .
a) Find the value of k .
b) Find the slope of the line.
c) Write the direct variation equation.
d) Graph the equation.
e) Find y when x = 24 .
f) Find x when y = 9 .
12. Suppose y varies directly as x , and y = 5 when x = 2 .
a) Find the value of k .
b) Find the slope of the line.
c) Write the direct variation equation.
d) Graph the equation.
e) Find y when x = 8 .
f) Find x when y = 20 .