At 10 am a plane leaves Boston MA for Seattle WA a distance

At 10 am a plane leaves Boston MA, for Seattle, WA, a distance of 3000 miles. One hour later a plane leaves Seattle for Boston. Both planes are traveling at a speed of 500 mph. How many hours after the plane leaves Seattle will the planes pass each other?

Solution

When the 2nd plane takes off, the 1st is 2500 miles away.
Their combined speed is 1000 mph, so they\'ll cover the distance in 2.5 hours (2500/1000).
----------
--> 2.5 hours after the 2nd plane leaves Seattle.