Direct Inverse Joint and Combined Variation

What kind of variation does this represent?

• Inverse variation

• Direct variation

• Joint variation

• Combined variation

What type of variation is y=k/x ?

• Joint

• Combined

• Inverse

• Direct

y varies jointly as x and z

• y=kx/z

• y=kxz

• y=kz/x

• y=k+x+z

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

The speed of a gear varies inversely as the number of teeth it has. If a gear with 24 teeth rotates of a speed of 45 revolutions per minute, how many revolutions per minute will a gear with 36 teeth make?

• 50

• 25

• 18

• 30

Suppose p varies directly as r, and inversely as t.

t = 20 when p = 4 and r = 2.

Find t when r = 10 and p = -5.

• 80

• -80

• 4

• -20

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 j varies inversely with m².

If j = 60 when m = 0.5 , find j when m = 5

• 0.6

• 9.6

• 400

• -400

Suppose f varies directly as g, and inversely as h.

f = -12 when h = 4 and g = -3.

Find g when f = 28 and h = 8.

• 14

• -14

• 16

• -16