Question 94101
To solve this problem use the distance formula that says the distance traveled is equal to 
speed times the time.
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[Think of a car. If you go at 60 miles per hour times 2 hours, how many miles do you go???
Pretty easy to see that the answer is 120 miles which comes from 60 times 2 hrs.]
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Call the speed of one plane S. And since the other plane is going twice as fast, its speed is 2S.
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Each plane flies for 3 hours.
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The distance the first plane goes in 3 hours is its speed S times 3 hours which means it covers
a distance of 3S.
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The distance the second plane goes in 3 hours is its speed 2S times 3 hours which means
it covers a distance of 6S.
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The total distance that  the planes cover is the sum of these two distances, 3S and 6S
and this equals 9S
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But the problem says the total distance between the two planes is 2700 miles.
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So we can write the equation:
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{{{9S = 2700}}}
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Then solve for S by dividing both sides of this equation by 9 to get:
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{{{S = 2700/9 = 300}}}
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So one plane is going 300 miles per hour and the second plane, going twice as fast is
going 600 miles per hour.
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In 3 hours the first plane goes 300*3 = 900 miles. And in the same 3 hours the second plane
goes 600*3 = 1800 miles. This makes the total distance between the (because they are going
in opposite directions) 900 + 1800 = 2700 miles, just as the problem said it would be.
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So the answer checks out ... 300 mph and 600 mph.
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Hope this helps you see your way through the problem.
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