Direct Proportionality

Y varies directly as x. If y = 12 when x = 15, what is y when x = 20?

• 4/5

• 17

• 16

• 25

n varies directly with c. If c = 24 when n = 18, what is c when n = 22?

• 88/3

• 28

• 66/4

• 24

Which equation exhibits a direct proportion?

• y = 5x - 2

• y = 3/4 x

• y - x = 4

• x = 6

Which equation is not an example of direct proportion?

• y = x

• y = 3x

• y = - 6x

• y = 2/3 x + 5

What is the value of k in the following equation? y = 2/7 x

• 4

• -4

• 2/7

• 7

For an equation to be directly proportional, it must .......

• pass thru two points

• pass thru the origin

• be positive

• not have a fraction

Upon seeing, "y varies directly as x" we immediately.....

• write down what x and y are

• write down what k is equal to

• substitute into the equation

• write y = kx

What means the same thing as direction proportion

• x = y

• direct variation

• y = k + x

• scale up proportion

Y varies directly as x. If y = 39 when x = 52, what is the best answer for k?

• k = 52

• k = 4/3

• k = 3/4

• k = 39/52

If x = 9 when y = 30, and x = 27 when y = 90, does y vary directly with x? If so, what is k equal to

• Yes, k = 10/3

• no

• Yes, k = 3/1

• Yes, k = 9