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.
Plane's Altitude
Time (minutes), x Altitude (feet), y
5 40,000
10 30,000
15 20,000
20 10,000
25 0
To find the rate of descent, we need to determine the change in altitude for each 5-minute interval.
From 5 to 10 minutes, the altitude decreases from 40,000 feet to 30,000 feet, a change of 10,000 feet.
From 10 to 15 minutes, the altitude decreases from 30,000 feet to 20,000 feet, a change of 10,000 feet.
From 15 to 20 minutes, the altitude decreases from 20,000 feet to 10,000 feet, a change of 10,000 feet.
From 20 to 25 minutes, the altitude decreases from 10,000 feet to 0 feet, a change of 10,000 feet.
Since the descent rate is constant, the rate of descent is equal for each 5-minute interval. Therefore, the rate of descent is 10,000 feet / 5 minutes, or 2,000 feet per minute.