document.write( "Question 79144This question is from textbook
\n" ); document.write( ": Marine travel. Sandy's tugboat moves at a rate of 10 mph in still water. It travels 24 miles upstream and 24 miles downstream in a total time of 5 hours. What is the speed of the current? \n" ); document.write( "
Algebra.Com's Answer #56818 by ankor@dixie-net.com(22740)\"\" \"About 
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Marine travel. Sandy's tugboat moves at a rate of 10 mph in still water. It travels 24 miles upstream and 24 miles downstream in a total time of 5 hours. What is the speed of the current?
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\n" ); document.write( "Let c = speed of the current:
\n" ); document.write( "Then:
\n" ); document.write( "Speed upstream = (10-c)
\n" ); document.write( "Speed downstream = (10+c)
\n" ); document.write( ":
\n" ); document.write( "Time = Distance/Speed
\n" ); document.write( ":
\n" ); document.write( "Time upstream + Time downstream = 5 hrs
\n" ); document.write( "\"24%2F%28%2810-c%29%29\" + \"24%2F%28%2810%2Bc%29%29\" = 5
\n" ); document.write( ":
\n" ); document.write( "Multiply equation by (10-c)(10+c); get rid of the denominators:
\n" ); document.write( "24(10+c) + 24(10-c) = 5(10+c)(10-c)
\n" ); document.write( ":
\n" ); document.write( "240 + 24c + 240 - 24x = 5(100 - c^2)
\n" ); document.write( "480 = 500 - 5c^2
\n" ); document.write( "5c^2 = 500 - 480
\n" ); document.write( "5c^2 = 20
\n" ); document.write( "c^2 = 20/5
\n" ); document.write( "c = Sqrt(4))
\n" ); document.write( "c = 2 mph is the current
\n" ); document.write( ":
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\n" ); document.write( "Check by finding the times, upstream & down stream
\n" ); document.write( "24/(10-2) = 3 hrs
\n" ); document.write( "24/(10+2) = 2 hrs
\n" ); document.write( "Total time= 5 hrs
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