document.write( "Question 257275: John has a boat that will travel at the rate of 15 kph in still water. He can go upstram for 35 km in the same time it takes to go 140 km downstream. How fast is his boat traveling when he goes downstream? \n" ); document.write( "

Algebra.Com's Answer #189253 by ankor@dixie-net.com(22740) $\"\"$ $\"About$

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John has a boat that will travel at the rate of 15 kph in still water.
\n" ); document.write( " He can go upstram for 35 km in the same time it takes to go 140 km downstream.
\n" ); document.write( " How fast is his boat traveling when he goes downstream?
\n" ); document.write( ":
\n" ); document.write( "Find the current first
\n" ); document.write( "Let c = speed of the current
\n" ); document.write( "then
\n" ); document.write( "(15-c) = speed upstream
\n" ); document.write( "and
\n" ); document.write( "(15+c) = speed downstream
\n" ); document.write( ":
\n" ); document.write( "Write a time equation; Time = dist/speed
\n" ); document.write( ":
\n" ); document.write( "Time down = time up
\n" ); document.write( " $\"140%2F%28%2815%2Bc%29%29\"$ = $\"35%2F%28%2815-c%29%29\"$
\n" ); document.write( "Cross multiply
\n" ); document.write( "35(15+c) = 140(15-c)
\n" ); document.write( ":
\n" ); document.write( "525 + 35c = 2100 - 140c
\n" ); document.write( ":
\n" ); document.write( "35c + 140c = 2100 - 525
\n" ); document.write( ":
\n" ); document.write( "175c = 1575
\n" ); document.write( "c = $\"1575%2F175\"$
\n" ); document.write( "c = 9 km/hr is the current
\n" ); document.write( "then
\n" ); document.write( "15 + 9 = 24 km/hr his speed downstream
\n" ); document.write( ";
\n" ); document.write( ":
\n" ); document.write( "Check solution by finding the times
\n" ); document.write( "140/24 = 5.83 hrs
\n" ); document.write( "35/6 = 5.833 hrs \n" ); document.write( "

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