Question

A jet departs from an airport flying east. At the same time, a second jet departs from the same airport flying west at a speed of 20 miles per hour slower than the first jet. After 1.5 hours, the planes are 1,500 miles apart. What is the speed in miles per hour of the jet traveling east?

A. 300

B. 750

C. 510

D. 490

Answer 1

510 miles

Explanation:

Please kindly check the attached file for explanation.

Answer 2

490mph and 510mph

Explanation:

Let x mph and x+20 mph be the speeds of the planes. The rate at which their distance from each other increases will be the sum of their speeds which is 2x+20 mph.

Their distance from each other after three hours is ( 1.5 hours)*(2x+20 mph) = 3x+30 miles. We are given that this is 1500 miles so we can solve for x.

3x+30 = 1500

3x = 1500 - 30

3x = 1470

x = 1470/3

x = 490mph

For the second jet :

x +20 = 490+20

x = 510

Thus the speeds of the two planes are 490 mph and 510mph.