Direct Inverse and Joint

y varies directly with x. If y=20 when x=4, what is y when x=-2?

• -10

• 10

• -5

• 5

In a direct variation, y = 39 when x = 3.

Find the value of y when x = 2.

• 24

• 15

• 26

• 29

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

• 6

• 121

• 100

• 4

Suppose y varies inversely with x.

If y = 150 when x = 2, find y when x = 25.

• 300

• 75

• 28

• 12

Which of the following represents indirect variation?

• y = kx

• y = x/k

• y = k/x

• y = mx + b

Is this a direct variation?

y=2x

• yes

• No

The time to prepare a field for planting is inversely proportional to number of people who are working.

A large field can be prepared by five workers in 24 days. In order to finish the field sooner, the farmer plans to hire additional workers.

How many workers are needed to finish the field in 15 days?

• 6 workers

• 8 workers

• 4 workers

• 10 workers

• direct variation
• inverse variation
• neither direct nor inverse variation

The equation 
xy =  25  represents:

• direct variation

• inverse variation

• joint variation

• none of these

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