Inverse Relationships

Which of the statements describes an inverse variation?

• an increase in x causes a decrease in y

• an increase in x causes an increase in y

Determine the type of variation:

• Direct
• Inverse
• Neither

What is the constant (k) in this inverse variation?
y = 400/x

• x
• y
• 400
• Not enough information given

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

• 121

• 4

• 100

• 6

When Darcy's school bus travels at 30 miles per hour, it gets from her home to school in 12 minutes. What is the speed of Darcy's bus if it makes the same trip in 18 minutes?  

• 45 mph
• 36 mph
• 28 mph
• 20 mph

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

Is the given table a direct or inverse variation? What is the constant of variation?

• Direct, 12
• Inverse, 12
• Direct, 1/12
• Inverse, 1/12

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

• 4
• 14 
• 7
• 28

True or False:
An inverse variation is always a curve and a direct variation is always a line?

• True
• False

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