A plane leaves an airport and flies south at 120 mph. Later, a second plane leaves the same airport and flies south at 300 mph. If the second plane overtakes the first one in
3.5hours, how much of a head start (in hr) did the first plane have?
since
the 2nd plane is 180 mi/hr faster
distance = speed * time,
it had a head start of 3.5 * 180 = 630 mi
630mi / (120 mi/hr) = 5.25 hr