Algebra Chapter 5 Section 2 Practice
Does the equation represent a direct variation? If so, find the constant of variation.
1.
2.
3.
4. Suppose y varies directly with x, and y = 10 when x = –3. What direct variation equation relates x and y? What is
the value of y when x = –1?
5. Suppose y varies directly with x, and y = 8 when x = –6. What direct variation equation relates x and y? What is the
value of y when x = –2?
6. Suppose y varies directly with x, and y =
19
4
when x = . What direct variation equation relates x and y? What is
3
5
7
the value of y when x =  ?
6
7. An enclosed gas exerts a pressure P on the walls of a container. This pressure is directly proportional to the
temperature T of the gas, measured in Kelvin. If the pressure is 7 lb per square inch when the temperature is 420ºK,
find the constant of variation and draw the graph of the equation.
8. The number of sofas a factory produces varies directly with the number of hours the machinery is operational.
Suppose the factory can produce 455 sofas in 48 hours. What is an equation that relates the number of sofas
produced, n, with the amount of time, t, in hours? What is the graph of your equation?
9. The grade a student makes on a test varies directly with the amount of time the student spends studying. Suppose a
student spends 5.5 hours studying and makes a grade of 76% on the test. What is an equation that relates the grade
earned on a test, g, with the amount of time spent studying, t, in hours? What is the graph of your equation?
For the data in the table, does y vary directly with x? If it does, write an equation for the direct variation.
10.
x
8
16
24
y
11
22
33
x
16
32
48
y
4
16
36
11.
Algebra Chapter 5 Section 2 Practice
Answer Section
5
3
10 10
4. y =  x;
3
3
1. yes; k = 
1
2
2.
yes; k =
5.
y = –1.33x; 2.67
7.
3.
no
6.
y=
95
665
x; 
12
72
8.
y
n
9
210
8
180
7
number of sofas
pressure (lb/sq in.)
10
6
5
4
3
2
150
120
90
60
30
1
10
20
30
40
50
60
70
80
90
8
9
x
temperature (K)
9.
100
g
90
80
grade
70
60
50
40
30
20
10
1
2
3
4
5
6
7
time (h)
10. yes; y = 1.375x
11. no; y does not vary directly with x
t
10
20
30
40
time (h)
50
60
70
t