Answer:
D. d = 2.05r
Explanation:
Distance, d, is a function of the number of rotations, r.
The relationship between the distance and the number of rotation is a direct proportion.
A direct proportion is represented by an equation of the form:
y = kx
where k is the constant of proportionality.
Here you are asked to use d and r instead of y and x, so you have:
d = kr
You are given one point in the graph of this relation: (400, 820).
Replace r with 400 and d with 820 and solve for k.
820 = k * 400
820 = 400k
400k = 820
Divide both sides by 400.
k = 820/400
k = 2.05
Now that we know the constant of proportionality, k, we plug it into the equation to get:
d = 2.05r