Direct Inverse Joint and Combined Variation

Solve for the constant of variation, k.

A varies directly as D and inversely as F. A=10.5, when D=2 and F=4

In a direct variation, y = 39 when x = 3. 
Find the value of y when x = 2.

• 26

• 3

• 58.5

• 2

The amount of money earned on a job is directly proportional to the number of hours worked. if $36 is earned for 8 hours of work, how much is earned for 30 hours of work?

• 135

• 6.667

• 1080

A dishwasher uses 65 gallons of water to wash 5 loads of dishes. What is the constant of variation?

• k = 13

• k = 65

• k = 5

• k = 1/13

Write the given statement in a mathematical equation.

r varies jointly as s and w

• r = ksw

• w = ksr

Solve for the constant of variation, k. y varies jointly as x and z.   x = -2 when y = 24 and z = -4

The variable x is in joint variation with y and z. When the values of y and z are 4 and 6, respectively, x is 72. What is the value of x when y = 2 and z =8?

• 32

• 48

• 64

• 96

A is in joint variation with B and square of C. When A = 144, B = 4 and C = 3. Then what is the value of A when B = 6 and C = 4?

• 12

• 36

• 384

• 96

z varies jointly with x and y. If x = 5, y = -1, and z = 10. Find z when x = -1 and y = 7.

• 14

• 7

• -21

• -7

If y varies jointly with the product of x and z, and y = 1000 when x = 10 and z = 20, find y when x = 8 and z = 10.

• 100

• 300

• 200

• 400