8.5E: Direct Variation

Given that y varies directly as x and y = -6 when x = 2; find the value of y when x = 14.

k = -3 y = -42

Does this equation represent direct variation? y = -6x - 6

No

Does this equation represent direct variation? y = 2x + 3

No

Does this equation represent direct variation? y = -9x

Yes

Does this equation represent direct variation? y = 1/4x

Yes

Heather's weekly pay is directly proportional to the number of hours she works at the record store. Her pay is $174 for 24 hours of work. Find the amount of pay for 40 hours of work.

k = $7.25 $290

Given that y varies directly as x and y = 4 when x = 16; find the value of y when x = 20.

k = 1/4 y = 5

y varies directly as x. If x = 5 when y = 12 find x when y = 30.

k = 12/5 x = 12.5

If y = -7 when x = -14, write the direct variation equation and find y when x = 20.

y = 0.5x; y = 10

If y = 10 when x = 9, write the direct variation equation and find x when y = 9.

y = 10/9x; x = 8.1

If y = 8 when x = 4, write the direct variation equation and find y when x = 5.

y = 2x; y = 10

If x = -7 when y = -14, write the direct variation equation and find y when x = 20.

y = 2x; y = 40

If y = 27 when x = 6, write the direct variation equation and find x when y = 45.

y = 4.5x; x = 10