document.write( "Question 1180672: The speed of a boat in still water is 15 km/hr. It goes 3 km upstream and returndownstream to the original point in 4 hrs 30 minutes.Find the speed of the stream. \n" ); document.write( "

Algebra.Com's Answer #810413 by greenestamps(13200) $\"\"$ $\"About$

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\n" ); document.write( "The numbers look unreasonable. Only 3km upstream and back in 4.5 hours means the speed of the stream must be nearly equal to the speed of the boat.

\n" ); document.write( "In any case....

\n" ); document.write( "x = speed of stream
\n" ); document.write( "15+x = downstream speed
\n" ); document.write( "15-x = upstream speed
\n" ); document.write( "3/(15+x) = downstream time
\n" ); document.write( "3/(15-x) = upstream time

\n" ); document.write( "The total time is 4.5 hours:

\n" ); document.write( " $\"3%2F%2815%2Bx%29%2B3%2F%2815-x%29=4.5\"$

\n" ); document.write( "With the suspicious numbers, I wouldn't even try solving that algebraically. I would graph the two functions $\"3%2F%2815%2Bx%29%2B3%2F%2815-x%29\"$ and $\"4.5\"$ on a graphing calculator and find where they intersect.

\n" ); document.write( " $\"graph%28400%2C400%2C-1%2C15%2C-1%2C5%2C3%2F%2815%2Bx%29%2B3%2F%2815-x%29%2C4.5%29\"$

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