Direct Inverse Joint and Combined Variation

Suppose y varies directly as x, and y=39 when x=3.  Find the value of y when x=2.

• 26

• 3

• 58.5

• 2

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

Suppose p varies directly as r, and p varies inversely as t.
t = 20 when p = 4 and r = 2.
Find t when r = 10 and p = -5.

• 80

• -80

• 4

• -20

The image is an example of the graph of a(n)

• direct variation

• inverse variation

• neither

• both

The horsepower (hp) that a shaft can safely transmit varies jointly with its speed (in revolutions per minute (rpm)) and the cube of the diameter. If the shaft of a certain material 3 inches in diameter can transmit 45 hp at 100 rpm, what must the diameter be in order to transmit 60 hp at 150 rpm?

• 24

The equation    
w = 10chs  represents:

• direct variation

• inverse variation

• joint variation

• none of these

w = 10chs  represents:

• direct variation

• inverse variation

• joint variation

• none of these

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

Suppose a varies jointly as b & c. 
If a = 15 when b = 4
and c = 5,
then find b when a = 60 and c = 5.

• 320

• 225

• 16

• 8