Answer: Yes it is a direct proportional relationship
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Step-by-step explanation:
The equation is in the form y = kx, where
x = number of sheets of paper
k = weight of 1 sheet of paper
y = weight of all the x sheets of paper
x is some nonnegative whole number. The values of y and k are some nonnegative real numbers (aka any decimal values).
Note how if we had x = 0 pieces of paper, then y = 0 is the weight. So no paper leads to no weight. This visually is shown by the line y = kx going through the origin. All direct proportion equations go through the origin.
Each time we add a sheet of paper, we add on k ounces or k grams, or whatever units you're working with. The amount is constant assuming you are dealing with the same type of paper. Comparing y = kx with y = mx+b, we see that k plays the role of the slope or rate of change.