The table shows how an elevator 500 feet above the ground is descending at a steady rate.

A two column table with 5 rows. The first column, time in seconds (t), has the entries, 0, 5, 10, 15. The second column, Height in feet h(t), has the entries, 500, 475, 450, 425.
Which equation represents the height, h(t), of the elevator in feet, as a function of t, the number of seconds during which it has been descending?

h(t) = 5t + 500
h(t) = 5t – 500
h(t) = –5t + 500
h(t) = –5t – 500

1 answer

To determine the correct equation representing the height \( h(t) \) of the elevator as a function of the time \( t \), we can analyze the provided data in the table.

From the table:

  • At \( t = 0 \) seconds, \( h(0) = 500 \) feet
  • At \( t = 5 \) seconds, \( h(5) = 475 \) feet
  • At \( t = 10 \) seconds, \( h(10) = 450 \) feet
  • At \( t = 15 \) seconds, \( h(15) = 425 \) feet

We observe that the elevator descends by 25 feet every 5 seconds. Therefore, the rate of descent can be calculated as follows:

\[ \text{Rate of descent} = \frac{25 \text{ feet}}{5 \text{ seconds}} = 5 \text{ feet per second} \]

Since the elevator is descending, the height decreases over time. This means that for every second that passes, the height decreases by 5 feet.

Thus, we can express this relationship mathematically. The height \( h(t) \) as a function of time \( t \) can be modeled with the following equation:

\[ h(t) = -5t + 500 \]

This equation tells us that at \( t = 0 \) seconds, the height is 500 feet, and for every additional second \( t \), the height decreases by 5 feet.

Now, we can check which of the options given matches this equation:

  1. \( h(t) = 5t + 500 \) ⇒ Incorrect, as this would imply the height increases.
  2. \( h(t) = 5t - 500 \) ⇒ Incorrect, as this does not match our calculated relationship.
  3. \( h(t) = -5t + 500 \) ⇒ Correct.
  4. \( h(t) = -5t - 500 \) ⇒ Incorrect, as this does not correctly account for the starting height.

Therefore, the correct equation is:

\[ \boxed{h(t) = -5t + 500} \]