Direct or Inverse Variation

If y varies inversely as x and x=5 when y=20, then what is the constant of variation, k? 

• 121

• 4

• 100

• 6

Assume y varies inversely with x. If x=7 when y=4, what is y when x=2 ?

• 4

• 14 

• 7

• 28

Write an equation for this relationship.

• y=4x

• y=1/8x

• y=1/4x

• y=8x

Is the given table a direct variation? If so, what is the constant?

• Yes; 1/4

• Yes; 4

• Yes; 2

• No

Is the following graph direct, inverse, or neither?

• Direct

• Inverse

• Neither

Is the following graph direct, inverse, or neither?

• Direct

• Inverse

• Neither

In a direct variation, y=39 when x=3.  Find the value of y when x=2.

• 26

• 3

• 58.5

• 2

The volume V of a gas kept at a constant temperature varies inversely as the pressure p.
If the pressure is 24 pounds per square inch, the volume is 15 cubic feet.
What will be the volume when the pressure is 30 pounds per square inch?

• 8 cubic feet

• 10 cubic feet

• 12 cubic feet

• 14 cubic feet

Suppose y varies inversely with x.
If y = 150 when x = 2, find y when x = 25.

• 300

• 75

• 1,875

• 12

The number of kilograms of water in a person’s body varies directly as the person’s mass.  A person with a mass of 90 kg contains 60 kg of water.  How many kilograms of water are in a person whose mass is 75 kg?

• 50 kg water

• 72 kg water

• 94 kg water

• 150 kg water