Question

Two planes, which are 1570 miles apart, fly toward each other. Their speeds differ by 85mph. If they pass each other in 2 hours, what is the speed of each?

Answer 1

• 350 mph
• 435 mph

Explanation:

You want to know the speeds of two planes, initially separated by 1570 miles, that pass each other after 2 hours. Their speeds differ by 85 mph.

Setup

Let x and y represent the speeds of the two planes in miles per hour (x>y). The relationship between time, speed, and distance is ...

speed = distance/time

Then the relations between the speeds are ...

x +y = (1570 mi)/(2 h)

x -y = 85 mi/h

Solution

Subtracting the second equation from the first, we have ...

(x +y) -(x -y) = (1570/2 -85) mph

2y = 700 mph . . . . . simplify

y = 350 mph . . . . . . divide by 2

x = (350 +85) mph = 435 mph

The speeds of the two planes are 350 mph and 435 mph.