document.write( "Question 106209: A passenger train can travel 325 mi in the same time a freight train takes to travel 200 mi. If the speed of the passenger train is 25 mi/h faster than the speed of the freight train, find the speed of each. \n" ); document.write( "
Algebra.Com's Answer #77255 by bucky(2189)\"\" \"About 
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To solve this problem, use the distance formula:
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\n" ); document.write( "D = R*T
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\n" ); document.write( "where D represents the distance traveled, R represents the rate or speed, and T represents
\n" ); document.write( "the amount of Time that the travel takes place.
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\n" ); document.write( "Before you begin recognize that if the speed of the freight train is F mph, then the speed of
\n" ); document.write( "the passenger train is F + 25 mph.
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\n" ); document.write( "Now we can write two equations. The distance that the passenger train travels is 325 miles.
\n" ); document.write( "The speed at which it travels is F + 25. And the time it travels is T. So its equation is:
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\n" ); document.write( "325 = (F+25)*T
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\n" ); document.write( "And the distance that the freight train travels is 200 miles. Its speed is F. And the time
\n" ); document.write( "it travels is also T. So its distance equation is:
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\n" ); document.write( "200 = F*T
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\n" ); document.write( "Suppose we solved both these equations for T. In the first equation we would divide both
\n" ); document.write( "sides by (F+25) and we would get that:
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\n" ); document.write( "\"T+=+325%2F%28F%2B25%29\"
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\n" ); document.write( "In the second equation we would solve for T by dividing both sides by F to get:
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\n" ); document.write( "\"T+=+200%2FF\"
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\n" ); document.write( "But the problem tells us that the two times ... the time the passenger train travels
\n" ); document.write( "is the same amount of time as the freight train travels. Therefore the two left sides (which
\n" ); document.write( "are both T) are equal. Therefore, we know that the two right sides must be equal also. So
\n" ); document.write( "we can set the two right sides equal and this equation becomes:
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\n" ); document.write( "\"325%2F%28F%2B25%29+=+200%2FF\"
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\n" ); document.write( "Let's multiply both sides by \"%28F%2B25%29%2AF\"
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\n" ); document.write( "\"%28%28F%2B25%29%2AF%2A+325%29%2F%28F%2B25%29+=+%28%28F%2B25%29%2AF%2A200%29%2FF\"
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\n" ); document.write( "Cancel the terms in the numerators with the same term in the denominator:
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\n" ); document.write( "and the equation reduces to:
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\n" ); document.write( "\"325F+=+200%28F%2B25%29\"
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\n" ); document.write( "Multiply out the right side by multiplying 200 times each of the terms in the parentheses
\n" ); document.write( "to get:
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\n" ); document.write( "\"325F+=+200F+%2B+5000\"
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\n" ); document.write( "Get rid of the 200F on the right side by subtracting 200F from both sides to reduce the
\n" ); document.write( "equation to:
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\n" ); document.write( "\"125F+=+5000\"
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\n" ); document.write( "Solve for F by dividing both sides by 125 and you have:
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\n" ); document.write( "\"F+=+5000%2F125+=+40\"
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\n" ); document.write( "This tells you that the speed of the freight train is 40 mph. Since the speed of the passenger
\n" ); document.write( "train is 25 mph faster, its speed is 40 + 25 = 65 mph.
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\n" ); document.write( "You can check these answers by noting that at 40 mph it will take the freight train 5
\n" ); document.write( "hours to go 200 miles. And at 65 mph in 5 hours the passenger train goes 5 * 65 = 325 miles.
\n" ); document.write( "Everything checks.
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\n" ); document.write( "Hope this helps you to understand this problem and shows you a way of working through it
\n" ); document.write( "to get the answer.
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