Question

Two planes, which are 2940 miles apart, fly toward each other. Their speeds differ by 35mph. If they pass each other in 4 hours, what is the speed of each?

Answer 1

• 385 mph
• 350 mph

Explanation:

You want the individual speeds of airplanes that close the 2940 mile distance between them in 4 hours, and have a speed difference of 35 mph.

Setup

The closing speed is found using the relation ...

speed = distance/time

It is ...

(2940 mi)/(4 h) = 735 mi/h

If x represents the speed of the slower plane, then (x+35) is the speed of the faster one. The sum of their speeds is the closing speed:

x +(x +35) = 735

Solution

Simplifying, we have ...

2x +35 = 735

2x = 700 . . . . . . subtract 35

x = 350 . . . . . . . divide by 2

x+35 = 385 . . . . speed of the faster plane

The speeds of the planes are 350 mph and 385 mph.