Question

A graph has time (hours) on the x-axis and Total costs (dollars) on the y-axis. Points are at (4, 52), (5, 60), (6, 68) and (7, 76).
The graph shows the charges of an instructor. The instructor charges an initial fee and then an hourly rate for private lessons. Determine the instructor's hourly charge from the graph.

What is the hourly charge?
$1.00
$4.00
$7.00
$8.00

Answer 1

To determine the instructor's hourly charge from the graph, we can analyze the given points:

- The points on the graph are:
- (4, 52)
- (5, 60)
- (6, 68)
- (7, 76)

Here, the x-coordinates represent time in hours, and the y-coordinates represent the total costs in dollars.

Let’s calculate the change in total cost as time increases by 1 hour:

1. From 4 hours to 5 hours:
\[
\text{Cost at 5 hours} - \text{Cost at 4 hours} = 60 - 52 = 8 \text{ dollars}
\]

2. From 5 hours to 6 hours:
\[
\text{Cost at 6 hours} - \text{Cost at 5 hours} = 68 - 60 = 8 \text{ dollars}
\]

3. From 6 hours to 7 hours:
\[
\text{Cost at 7 hours} - \text{Cost at 6 hours} = 76 - 68 = 8 \text{ dollars}
\]

In each case, the increase in total cost per hour is $8.00.

Thus, the instructor's hourly charge is **$8.00**.

The correct answer is $8.00.