Name:    Direct, Inverse, and Joint Variation

Multiple Choice
Identify the choice that best completes the statement or answers the question.

1.

If y varies directly as x and y = 9 when x = –3, find y when x = 18.
 a. 54 c. 486 b. –54 d. –486

2.

Suppose y varies jointly as x and z. Find y when x = 2 and z = 25, if y = 205 when x = 7 and z = 10.
 a. 146 c. 287 b. 1,464 d. 146

3.

If y varies inversely as x and y = 107 when x = –12, find y when x = 2.
 a. –17.83 c. 642 b. 17.83 d. –642

4.

Which equation shows that z is directly proportional to the square root of x and inversely proportional to the cube of y?
 a. c. b. d.

5.

The volume of a gas varies directly as its temperature and inversely as its pressure. Alison is working with a gas in a laboratory at Lynchburg College. At a temperature of 375 Kelvin and a pressure of 25 pascals, she measured the volume of this gas as 30 cubic centimeters. What volume should she expect if she decreases the temperature to 320 Kelvin and increases the pressure to 40 pascals?
 a. 4 cm3 c. 16 cm3 b. 8 cm3 d. 46.875 cm3