Distance rate time

Question

Two trains leave the station at the same time, one heading east and one west. The eastbound train travels 10 miles per hour slower than the westbound train. If the two trains are 640 miles apart after 4 hours, what is the rate of the east bound train? Do not do any rounding

Answer 1

Let x be the speed of the West bound train. 

Let x-10 be the speed of the East bound train. 

 

4(x + (x-10)) = 640

4(2x - 10) = 640

8x - 40 = 640

8x = 640 + 40

8x = 680

x = 680/8

x = 85 mph

 

Proof

4(85 + 75) = 640

4(160) = 640