document.write( "Question 165552: An increase of speed of 4km/h on a journey of 32km reduces the time taken by 4 hours. find the orginal speed? \n" ); document.write( "

Algebra.Com's Answer #122037 by ankor@dixie-net.com(22740) $\"\"$ $\"About$

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An increase of speed of 4km/h on a journey of 32km reduces the time taken
\n" ); document.write( " by 4 hours. find the original speed?
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\n" ); document.write( "Let s = original speed
\n" ); document.write( "then
\n" ); document.write( "(s+4) = the faster speed
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\n" ); document.write( "Write time equation; time = $\"distance%2Fspeed\"$
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\n" ); document.write( "original speed time - 4 hr = faster speed time
\n" ); document.write( " $\"32%2Fs\"$ - 4 = $\"32%2F%28%28s%2B4%29%29\"$
\n" ); document.write( ":
\n" ); document.write( "Multiply equation by s(s+4), results:
\n" ); document.write( "32(s+4) - 4s(s+4) = 32s
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\n" ); document.write( "Multiply what's inside the brackets
\n" ); document.write( "32s + 128 - 4s^2 - 16s = 32s
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\n" ); document.write( "-4s^2 - 16s + 128 = 0; subtracted 32s from both sides,
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\n" ); document.write( "Simplify, change the signs, divide equation by -4
\n" ); document.write( "s^2 + 4s - 32 = 0
\n" ); document.write( "Factor
\n" ); document.write( "(s + 8)(s - 4) = 0
\n" ); document.write( "Positive solution
\n" ); document.write( "s = 4 km/hr is the original speed
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\n" ); document.write( "Check solution finding the time of each (faster speed = 8 km/hr)
\n" ); document.write( "32/4 = 8 hrs
\n" ); document.write( "32/8 = 4 hrs
\n" ); document.write( "--------------
\n" ); document.write( "differ 4 hrs \n" ); document.write( "

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