An airplane is starting its descent to prepare for landing. The table shows the linear relationship between the number of minutes of descent and the altitude of the plane.

Question

Plane's Altitude

Time (minutes), x Altitude (feet), y
5 40,000
10 30,000
15 20,000
20 10,000
25 0

Which statement is true?
Responses
A The plane was descending at 2,000 feet per minute.The plane was descending at 2,000 feet per minute.
B The plane’s starting altitude was 40,000 feet.The plane’s starting altitude was 40,000 feet.
C The plane’s starting altitude was 45,000 feet. The plane’s starting altitude was 45,000 feet.
D The plane was descending at 25 feet per minute.

Answer 1

To analyze the data:

• At 5 minutes, the altitude is 40,000 feet.
• At 10 minutes, the altitude is 30,000 feet.
• At 15 minutes, the altitude is 20,000 feet.
• At 20 minutes, the altitude is 10,000 feet.
• At 25 minutes, the altitude is 0 feet.

From 5 to 10 minutes, the altitude decreases from 40,000 feet to 30,000 feet. This is a decrease of 10,000 feet over 5 minutes. Hence, the descent rate can be calculated as follows:

\[ \text{Descent rate} = \frac{\text{Change in altitude}}{\text{Time}} = \frac{10,000 \text{ feet}}{5 \text{ minutes}} = 2,000 \text{ feet per minute} \]

Let's evaluate the given statements:

A. The plane was descending at 2,000 feet per minute. (True)

B. The plane’s starting altitude was 40,000 feet. (True)

C. The plane’s starting altitude was 45,000 feet. (False)

D. The plane was descending at 25 feet per minute. (False)

Since both A and B are true, but the question asks which statement is true without further context, the best answer that matches the scenario is:

A. The plane was descending at 2,000 feet per minute.