direct and inverse variation word problems

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

Tags

CCSS.7.RP.A.2

CCSS.7.RP.A.3

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

Tags

CCSS.7.EE.B.3

CCSS.7.EE.B.4

CCSS.7.RP.A.2

CCSS.7.RP.A.3

Boyle’s Law states that, for a fixed amount of gas, the volume of the gas at a constant   temperature is inversely proportional to the pressure. If a certain gas occupies 9.84 liters   at a pressure of 50 centimeters of mercury (cm Hg), what is the approximate pressure   when the volume is increased to 12 liters?

• 39.8 cm Hg
• 41.0 cm Hg 
• 43.2 cm Hg
• 45.1 cm Hg

Tags

CCSS.7.EE.B.3

CCSS.7.EE.B.4

CCSS.7.RP.A.2

Suppose y varies directly as x.
If  y = 22.5 when x = 15, find y when x = 20.

• 1.5
• 337.5
• 30
• 16.875

Tags

CCSS.7.EE.B.4

CCSS.7.RP.A.2

If y varies directly as x and y = 15 when x = 12 find y when x = 32.

• 40

• -40

• 5

• -5

Tags

CCSS.7.EE.B.4

CCSS.7.RP.A.2

y varies directly as x, if y=4 when x=3, find x when y=-12

• -16
• 16
• -9
• 9

Tags

CCSS.7.EE.B.4

CCSS.7.RP.A.2

The time it takes to fly from Los Angeles to New York varies inversely as the speed of the plane. If the trip takes 6 hours at 900 km/h, how long would it take at 800 km/h?

• 5.33 hours 
• 6.75 hours 
• 12 hours 
• 10 hours 

Tags

CCSS.7.EE.B.3

CCSS.7.EE.B.4

CCSS.7.RP.A.2

CCSS.7.RP.A.3

The cost per person to rent a mountain cabin is inversely proportional (varies inversely) to the number of people who share the rent. If the cost is $36 per person when 5 people share, what is the cost per person when 8 people share?

• $22.50
• $57.60
• $1.11
• $12.50

Tags

CCSS.7.EE.B.3

CCSS.7.NS.A.2

CCSS.7.NS.A.3

CCSS.7.RP.A.2

CCSS.7.RP.A.3

Trina's paycheck earnings varies directly as the number of hours she works. If she works 19 hours and earns $187.15, what should she earn if she worked 40 hours? 

• $394
• $443.25
• $472.80
• $512.20

Tags

CCSS.7.EE.B.4

CCSS.7.RP.A.2

CCSS.7.RP.A.3

The gas pressure in a chamber varies directly with the temperature in the chamber. If the pressure in the chamber is 150 atmospheres (atm) when the chamber is at 50 degrees, what is the pressure in the chamber when the temperature of the chamber is 75 degrees? 

• 175 atm
• 200 atm
• 225 atm
• 275 atm

Tags

CCSS.7.EE.B.4

CCSS.7.RP.A.2

CCSS.7.RP.A.3