Direct and Inverse Proportions

The number of hours to paint a house varies inversely with the number of painters working. A 2400-square foot house can be painted in 27 hours by 6 painters. How many painters would need to work in order to paint the house in 18 hours?

• 8 painters

• 10 painters

• 9 painters

• 11 painters

The width of a rectangle varies inversely with its length. if the width is 4 when the length is 18, find the width when the length is 8.

• 9

• 72

• 36

• 2

g is directly proportional to b

Given g=20 when b=4.

Find g when b=7

• 35

• 5

• 15

• 23

What type of variation does this scenario represent?
The length of time you charge your cell phone
and the battery power 

• direct variation

• inverse variation

• joint variation

• none of these

What type of variation does this scenario represent?
The outside temperature
and the number of layers of clothes you need to wear outside to feel comfortable 

• direct variation

• inverse variation

• joint variation

• none of these

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

The amount of money spent at the gas station varies directly with the number of gallons purchased. When 9.5 gallons of gas were purchased the cost was $36.52. How much would 12 gallons of gas cost?

• Direct Variation

• Inverse Variation

The number of pencils sold varies directly as the cost. If 5 pencils cost $0.45, find the cost of 7 pencils.

• Direct Variation

• Inverse Variation

The time needed to travel a certain distance varies inversely with the rate of speed. If it takes 6 hours to travel a certain distance at 40 miles per hour, how long will it take to travel the same distance at 55 miles per hour?

• Direct Variation

• Inverse Variation

The number of centimeters y in a linear measurement varies directly with the number of inches x in the measurement. Pablo's height is 167.64 centimeters or 66 inches. What is Maria's height in centimeters if she is 63 inches tall?

• Direct Variation

• Inverse Variation