At 10 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 400 mph. How many hours after the plane leaves Seattle will the planes pass each other?

Question

Quizplus · Accepted Answer

The plane leaving Boston will have a one-hour head start, so we only need to consider how long it takes the two planes to cover the remaining distance between them. The combined speed of the two planes is 800 mph (400 mph from each plane), so the amount of time it takes for them to cover the remaining 2700 miles is:

time = distance / speed
time = 2700 / 800
time = 3.375 hours

However, we need to add the one-hour head start from Boston, so the total time is:

total time = 3.375 + 1
total time = 4.375 hours

Rounding to the nearest quarter hour gives us a final answer of 3.25 hours, or choice D.

At 10 AM a Plane Leaves Boston, Massachusetts, for Seattle, Washington, a Washington