An airplane left Miami, FL. At the same time another plane left Santiago, Chile. The two planes flew toward each other at rates of 625 mph and 575 mph. If Miami and Santiago are 4200 miles apart, how long will it take until the planes pass each other?

To solve the above question we use the concept of relative speed.

The rates of the two planes are 625 mph and 575 mph.

Relative speed will be:

[speed of plane A]+[speed of plane B]

=625+575

=1,200 mph

Distance=4200 miles

Thus the time taken for them to meet will be:

Time=distance/speed

=4200/1200

=3.5 hours

We therefore conclude that the planes met after 3.5 hours