Question

The graph shows the number of songs and the cost of downloading them. How many songs can be downloaded for $\$150?$

• A. $75$
• B. $85$
• C. $80$
• D. $70$

Answer 1

The correct option is A $75$

The graph is a straight line passing through the origin; hence, it represents a proportional relationship.
Download cost per song is nothing but the unit rate or the slope of the graph.
Let’s consider,
$x_1=5,y_1=10;x_2=10$, and $y_2=20$.
Unit rate $=\frac{\text{Rise}}{\text{Run}}=\frac{y_2-y_1}{x_2-x_1}=\frac{20-10}{10-5}=\frac{10}{5}=\$2/song$
Number of songs that can be downloaded for $\$150=\frac{150}{2}=75$