document.write( "Question 963050: Please help me solve this problem: A trip of 189 miles can take one hour less if gerald increases the average speed of his car by 12 miles per hour. What was the original average speed of the car? \n" ); document.write( "
Algebra.Com's Answer #588389 by ankor@dixie-net.com(22740)\"\" \"About 
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A trip of 189 miles can take one hour less if gerald increases the average speed of his car by 12 miles per hour.
\n" ); document.write( " What was the original average speed of the car?
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\n" ); document.write( "let s = the original speed
\n" ); document.write( "then
\n" ); document.write( "(s+12) = the increased speed
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\n" ); document.write( "Write a time equation, time = dist/speed
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\n" ); document.write( "Original time - faster time = 1 hr
\n" ); document.write( "\"189%2Fs\" - \"189%2F%28%28s%2B12%29%29\" = 1
\n" ); document.write( "multiply equation by s(s+12), cancel the denominators and you have
\n" ); document.write( "189(s+12) - 189s = s(s+12)
\n" ); document.write( "189s + 2268 - 189s = s^2 + 12s
\n" ); document.write( "Combine to form a quadratic equation on the right
\n" ); document.write( "0 = s^2 + 12s - 2268
\n" ); document.write( "you can use the quadratic formula; a=1; b=12; c=-2268
\n" ); document.write( "But this will factor to
\n" ); document.write( "(s+54)(s-42) = 0
\n" ); document.write( "the positive solution is what we want here\
\n" ); document.write( "s = 42 mph is the original speed
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\n" ); document.write( "Check this by finding the actual time at each speed.
\n" ); document.write( "189/42 = 4.5 hrs
\n" ); document.write( "189/54 = 3.5 hrs, 1 hr less \n" ); document.write( "
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