Sara is baking cookies, so she turns the oven on. As soon as Sara turns the oven on, the oven heats up at a constant rate. Write an equation to represent this situation. Then use the equation to make a prediction.

This graph represents the linear relationship between the time in minutes and the temperature of the oven in degrees Fahrenheit. For each minute, the temperature increases at a constant rate. What do the points (4, 120) and (14, 340) represent?
x
y
(4, 120)(14, 340)
0
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0
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Time (minutes)
Temperature (°F)
The point (4, 120) means that after
minutes, the oven’s temperature was
degrees Fahrenheit.

The point (14, 340) means that after
minutes, the oven’s temperature was
degrees Fahrenheit.

1 answer

To model the situation, we can write a linear equation that relates the time (x) in minutes to the temperature (y) in degrees Fahrenheit. Since the temperature increases at a constant rate, we can express the relationship as:

\[ y = mx + b \]

Where:

  • \( y \) is the temperature in degrees Fahrenheit.
  • \( x \) is the time in minutes.
  • \( m \) is the rate of temperature increase per minute.
  • \( b \) is the initial temperature of the oven when \( x = 0 \).

From the two points given:

  1. (4, 120): at 4 minutes, the temperature is 120°F.
  2. (14, 340): at 14 minutes, the temperature is 340°F.

Step 1: Find the rate of temperature increase (m)

We can find \( m \) using the formula for slope:

\[ m = \frac{y_2 - y_1}{x_2 - x_1} \]

Using the points (4, 120) and (14, 340):

  • \( y_1 = 120 \), \( x_1 = 4 \)
  • \( y_2 = 340 \), \( x_2 = 14 \)

\[ m = \frac{340 - 120}{14 - 4} = \frac{220}{10} = 22 \]

So, the oven temperature increases at a rate of 22°F per minute.

Step 2: Find the initial temperature (b)

To find \( b \), we can use one of the points in the equation. We'll use the point (4, 120):

\[ y = mx + b \] \[ 120 = 22(4) + b \] \[ 120 = 88 + b \] \[ b = 120 - 88 = 32 \]

The equation for the temperature of the oven:

Thus, our linear equation is:

\[ y = 22x + 32 \]

Interpret the given points

Now we interpret the points:

  • The point (4, 120) means that after 4 minutes, the oven’s temperature was 120 degrees Fahrenheit.

  • The point (14, 340) means that after 14 minutes, the oven’s temperature was 340 degrees Fahrenheit.

Feel free to ask if you have any further questions!