Question 522932
d = r*t is the basic distance equation.
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The first plane flies for 1 1/2 = 3/2 hr at 184 mph.
d = 3/2 * 184 = 3 * 92 = 276 miles
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The second also flies 276 miles to overtake the first plane
It does this at a rate of 460 mph.
So, it flies for a different amount of time.
t = d/r
t = 276/460 = 3/5 hr * 60 min/hr = 36 min 
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The first plane flies for 3/2 hr * 60 min/hr = 90 min
So its head start was 90-36 = 54 minutes.
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Done.