Question

A commercial jet and a private airplane fly from Denver to Phoenix. It takes the commercial jet 1.6 hours for the flight, and it takes the private airplane 2.4 hours.

The speed of the commercial jet is 180 miles per hour faster than the speed of the private airplane. Find the speed, in miles per hour, of both airplanes.
commercial jet
X mph
private airplane
X mph

Answer 1

• commercial: 540 mph
• private: 360 mph

Explanation:

Time is inversely proportional to speed for the same distance covered. The ratio of commercial to private speeds is ...

2.4 : 1.6 = 3 : 2

If p is the speed of the private plane, then 3/2p is the speed of the commercial plane and the difference of speeds is ...

3/2p -p = 180

1/2p = 180 . . . collect terms

p = 360 . . . . . . speed of the private plane

3/2p = 540 . . . . speed of the commercial plane

The commercial jet flies 540 mph; the private plane flies 360 mph.