Direct Variation

If y varies directly as x, and x = 9 when y = 15, find y when x = 33.

• 55

• 24

• 38

• 49

If c varies directly as the square root of d, and c = 14 when d = 64, find c when d = 324.

• 7

• 63/2

• 280

• 14/5

What is the direct variation equation if y = 8 and x = 4?

• y=x

• y=2x

• y=4x

• y=8x

What is the direct variation equation if y = –5 and x = 7?

• y=5x

• y=-(7/5)x

• y=-(5/7)x

• y=7x

Suppose y varies directly with x, and when y is 16, x is 8. Find y when x is 16.

• 24

• 32

• 48

• 64

Suppose y varies directly with x, and when y is 2, x is 3. Find x when y is 42.

• 21

• 35

• 49

• 63

This equation represents a direct variation: 2x=y

• True

• False

Which of the following is the equation that describes the variation: v varies directly with t; v = 16 when t = 2.

• v = kt

• v = k/t

• v = 8t

• v = 8/t

The distance required to stop a car varies directly as the square of its speed. If 250 feet are required to stop a car traveling 60 miles per hour, how many feet are required to stop a car traveling 96 miles per hour?

• 640 feet

• 320 feet

• 480 feet

• 720 feet

Your distance from a lightning bolt varies directly with the time it takes you to hear thunder. If you hear thunder 10 seconds after you see the lightning, you are about 2 miles from the lightning. How many seconds it will take for the thunder to travel a of 4 miles.

• 10 seconds

• 20 seconds

• 30 seconds

• 40 seconds