Question

An airplane begins it's descent to and from a height of 35,000 feet above ground level. the airplane's height decreases by about 4,000 feet every 3 minutes. Rounded to the nearest minute, in approximately how many minutes will the plane land ?

Answer 1

A formula for the height of the plane as a function of time (t, in minutes) would be

h(t) = 35000 ft - (4000 ft / 3 min)(t).

When will the plane land? Let h=0 and solve for t: 35000 = (4000/3)t
35000 ft
Solving for t, t = ------------------------ = 26 minutes (approx).
(4000/3) (ft/min)