An airplane has begun its descent for a landing. When the airplane is 150 miles west of its destination, its altitude is 25,000
feet. When the airplane is 90 miles west of its destination, its altitude is 19,000 feet. If the airplane's descent is modeled by a linear function, where will the airplane be in relation to the runway when it hits ground level?
The airplane has descended (25,000 - 19,000) = 6,000 feet while flying (150 - 90) = 60 miles.
If the descent is modeled by a linear function, then the slope of the function is
(-6000 ft) / (60 miles) = - 100 ft/mile .
Since it still has 19,000 ft left to descend, at the rate of 100 ft/mi, it still needs to fly
(19,000 ft) / (100 ft/mile) = 190 miles
to reach the ground.
It's located 90 miles west of the runway now. So if it continues on the same slope, it'll be 100 miles past the runway (east of it) when it touches down.