Question

The graph below represents the price of sending text messages using the services of a phone company. What is the constant of proportionality? A. 12 B. 24 C. 46. D. 48

Answer 1

Ah, direct variation/proportion.
That is simply a linear equation with a y-intercept of 0.
So... let's solve this.
Simply put, a direct variation multiplies the x-value by a constant to get the y-value.
Let's take the point $(2, 48)$ on this graph and solve for the constant of proportionality:
$2a=48$
We easily solve that and get our answer of $a=24$. (B)