Model Inverse and Joint Variation

The equation 
xy =  25  represents:

• direct variation

• inverse variation

• joint variation

• none of these

The equation    
w = 10chs  represents:

• direct variation

• inverse variation

• joint variation

• none of these

Suppose y varies jointly as x & z. 
If y = -180 when z = 15
and x = -3,
then find y when x = 7 and z = -5.

• -140

• 140

• -4

• 4

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

• 300

• 75

• 1,875

• 12

Y varies inversely with x, and y is 0.5 when x is 4. Which equation represents this situation?

• y=2x

• y=2/x

• y=4x

• y=x/2

If x and y are in an inverse variation then which of the following is correct?

• x - y = constant

• x + y = constant

• xy = constant 

• x⁄y is constant 

Given (32, 15) and (12, y). Find the constant k of inverse variation, and then find the missing y value.

• 40

• 48

• -40

• -48

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 cost per person to rent a mountain cabin 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

• $4.50

• $12.50