Which of the following has a constant of proportionality of 2? a) y = 2x b) y = x + 2 c) 2y = x d) y + 2 = 2x

The correct answer is A.

You have direct variation if x and y are modeled by the equation

In this case, m is the constant of proportionality. So, if the constant has to be 2, the equation becomes

A side note: Actually, option C has a constant of proportionality of two as well, except the roles of x and y are interchanged. I chose option A because usually you want the y = mx form, but the names of the variables are obviously meaningless.

The answer is A. 1.35

If you divide 2.3 by 1.7, you get 1.35.