Corey fills his bus with gas. The bus has some gas in it, and Corey fills it at a constant rate each minute. Write an equation that represents this situation. Then use the equation to make a prediction.

This graph represents the linear relationship between the time in minutes and the gallons of gas in the bus. For each minute, the gallons of gas increases at a constant rate. What do the points (4, 75) and (14, 175) represent?
x
y
(4, 75)(14, 175)
0
2
4
6
8
10
12
14
16
18
20
0
25
50
75
100
125
150
175
200
Time (minutes)
Gallons of gas
The point (4, 75) means that after
minutes, there are
gallons of gas in the bus.

The point (14, 175) means that after
minutes, there are
gallons of gas in the bus.

1 answer

Let's represent the situation with an equation first. We know that the relationship between the time (in minutes) and the gallons of gas in the bus is linear, meaning it can be described by the equation:

\[ g(t) = mt + b \]

Where:

  • \( g(t) \) is the number of gallons of gas in the bus after \( t \) minutes.
  • \( m \) is the rate at which gas is added per minute.
  • \( b \) is the initial amount of gas in the bus at \( t = 0 \).

From the points (4, 75) and (14, 175), we can derive the rate and the initial amount of gas.

  1. First, find the rate \( m \):

The change in gas over the change in time between the two points: \[ m = \frac{175 - 75}{14 - 4} = \frac{100}{10} = 10 \]

This indicates that Corey adds 10 gallons of gas each minute.

  1. Next, we can use one of the points to find the initial amount of gas \( b \). Let's use the point (4, 75).

Substituting \( m \) and the point (4, 75) into the equation: \[ 75 = 10(4) + b \] \[ 75 = 40 + b \] \[ b = 75 - 40 = 35 \]

Thus, the complete equation representing the number of gallons of gas in the bus after \( t \) minutes is:

\[ g(t) = 10t + 35 \]

Predictions using the equation:

To predict the number of gallons of gas after a specific time, we can plug in values of \( t \) into our equation.

Now, let's address the points (4, 75) and (14, 175):

  • The point (4, 75) means that after 4 minutes, there are 75 gallons of gas in the bus.
  • The point (14, 175) means that after 14 minutes, there are 175 gallons of gas in the bus.

To summarize:

  • (4, 75) means that after 4 minutes, there are 75 gallons of gas in the bus.
  • (14, 175) means that after 14 minutes, there are 175 gallons of gas in the bus.