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)![]() ![]() ![]() You can put this solution on YOUR website! To solve this problem, use the distance formula: \n" ); document.write( ". \n" ); document.write( "D = R*T \n" ); document.write( ". \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. \n" ); document.write( ". \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. \n" ); document.write( ". \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: \n" ); document.write( ". \n" ); document.write( "325 = (F+25)*T \n" ); document.write( ". \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: \n" ); document.write( ". \n" ); document.write( "200 = F*T \n" ); document.write( ". \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: \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( "In the second equation we would solve for T by dividing both sides by F to get: \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \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: \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( "Let's multiply both sides by \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( "Cancel the terms in the numerators with the same term in the denominator: \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( "and the equation reduces to: \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( "Multiply out the right side by multiplying 200 times each of the terms in the parentheses \n" ); document.write( "to get: \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \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: \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( "Solve for F by dividing both sides by 125 and you have: \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \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. \n" ); document.write( ". \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. \n" ); document.write( ". \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. \n" ); document.write( ". \n" ); document.write( " |