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At 7 A.M. a plane leaves Boston, Massachusetts, for Seattle, Washington, a distance of 3000 mi.
One hour later a plane leaves Seattle for Boston. Both planes are traveling at a speed of 300 mph.
How many hours after the plane leaves Seattle will the planes pass each other?
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How many hours after the plane leaves Seattle will the planes pass each other =
= = = 4.5 hours. ANSWER
Solved.
Guess why it is so.
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By the way, the time 7:00 am, mentioned in the problem, is not relevant to the question, at all.
Also, one more detail/feature for your education.
The distance between these cities for the plane flight is significantly different
from the distance between them on the Earth surface along the latitude.
Flight distance: 2,492 miles or 4011 km.
Nonstop drive: 3,056 miles or 4918 km.
Source: https://www.trippy.com/distance/Seattle-to-Boston
Why ? - Because the driving root is mostly along the latitude,
while the flight root is along the great circle along the Earth surface,
which is about 550 miles shorter: the difference 3,056 - 2,492 is 564 miles.
Also, notice that your post gives the driving distance between these cities instead of the flight distance.
It is because the person who composed this problem, actually, does not know the subject.
A side lesson to learn from my post:
The earth is not flat. It is spherical, and flight roots follow to the Earth' spherical form.