document.write( "Question 115248: Chuck and Dana agree to meet in Chicago for the weekend. Chuck travels 108 miles in the same time that Dana travels 99 miles. If Chuck's rate of travel is 3 mph more than Dana's, and they travel the same length of time, at what speed does Chuck travel? \n" ); document.write( "
Algebra.Com's Answer #83830 by bucky(2189)\"\" \"About 
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Use the formula that Distance equals Speed times Time to solve this equation. In equation
\n" ); document.write( "form this is:
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\n" ); document.write( "\"D+=+S%2AT\"
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\n" ); document.write( "For Chuck, the distance he traveled was 108 miles. His speed was \"S%5Bc%5D\" where the \"c\" indicates
\n" ); document.write( "it is Chuck's speed. Substituting these into the equation for chuck results in:
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\n" ); document.write( "\"108+=+S%5Bc%5D%2AT\"
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\n" ); document.write( "Solve this equation for T by dividing both sides by \"S%5Bc%5D\" to get:
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\n" ); document.write( "\"T+=+108%2FS%5Bc%5D\"
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\n" ); document.write( "Meanwhile, Dana travels 99 miles in the same time. Let \"S%5Bd%5D\" represent Dana's speed.
\n" ); document.write( "Substituting these values into the distance equation results in:
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\n" ); document.write( "\"99+=+S%5Bd%5D%2AT\"
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\n" ); document.write( "Solve this equation for T by dividing both sides by \"S%5Bd%5D\" and it becomes:
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\n" ); document.write( "\"T+=+99%2FS%5Bd%5D\"
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\n" ); document.write( "So we have two equations for T ... one for Chuck and one for Dana. But, according
\n" ); document.write( "to the problem, both drivers drive for equal times. So the two T equations are equal. That
\n" ); document.write( "means the right sides of these equations are equal for the two drivers. So it can be said
\n" ); document.write( "that:
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\n" ); document.write( "\"108%2FS%5Bc%5D+=+99%2FS%5Bd%5D\"
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\n" ); document.write( "Next the problem tells you that Chuck's speed is 3 miles per hour more than Dana's. So
\n" ); document.write( "it also can be said that:
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\n" ); document.write( "\"S%5Bc%5D+=+S%5Bd%5D+%2B+3\"
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\n" ); document.write( "Substitute the right side of this into the Time equation and the result is:
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\n" ); document.write( "\"108%2F%28S%5Bd%5D%2B3%29+=+99%2FS%5Bd%5D\"
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\n" ); document.write( "Put both of these fractions over a common denominator by multiplying both sides of this
\n" ); document.write( "equation by \"%28S%5Bd%5D%2A%28S%5Bd%5D+%2B3%29%29%2F%28S%5Bd%5D%2A%28S%5Bd%5D+%2B3%29%29\". Note that since the numerator of this
\n" ); document.write( "multiplier is equal to the denominator, this is equivalent to multiplying both sides of the
\n" ); document.write( "equation by 1.
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\n" ); document.write( "This multiplication leads to:
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\n" ); document.write( "Cancel the like terms in the denominators and numerators on both sides:
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\n" ); document.write( "This leaves:
\n" ); document.write( ".
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\n" ); document.write( "Since the denominators are the same on both sides, the numerators must be equal. So, setting
\n" ); document.write( "the numerators equal results in:
\n" ); document.write( ".
\n" ); document.write( "\"108%2AS%5Bd%5D=+99%2A%28S%5Bd%5D%2B3%29\"
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\n" ); document.write( "Multiplying out the right side results in:
\n" ); document.write( ".
\n" ); document.write( "\"108%2AS%5Bd%5D+=+99%2AS%5Bd%5D+%2B+297\"
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\n" ); document.write( "Subtract \"99%2AS%5Bd%5D\" from both sides to get rid of that term on the right side and the
\n" ); document.write( "result is:
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\n" ); document.write( "\"9%2AS%5Bd%5D+=+297\"
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\n" ); document.write( "Solve for \"S%5Bd%5D\" by dividing both sides by 9 to get:
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\n" ); document.write( "\"S%5Bd%5D+=+297%2F9+=+33\"
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\n" ); document.write( "So Dana's speed is 33 miles per hour. And Chuck's speed, which is 3 miles per hour faster,
\n" ); document.write( "is 36 miles per hour.
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\n" ); document.write( "Check. At 36 miles per hour it will take Chuck 3 hours to go 108 miles. And at 33 miles per
\n" ); document.write( "hour, it will take Dana 3 hours to go 99 miles. The answer checks because the times are equal.
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\n" ); document.write( "Hope this helps you to understand the problem and to see how it might be solved.
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