A train left mooseport traveling west at 50 mph. One hour later, another train left mooseport traveling east at 70 mph. How many hours had the first train been traveling when they were 350 miles apart.

Answer 1

the trains are separating at 70+50=120 mi/hr

When the 2nd train left, they were already 50 miles apart.

So, the remaining 300 miles will take 300/120 hours.

Add that to the original hour head-start.

Answer 2

Let the time for the first train be t hrs

50t + 70(t-1) = 350
120t = 420
t = 420/120 = 7/2 or 3.5 hrs