document.write( "Question 678025: A motorboat can maintain a constant speed of 16mph relative to the water. The boat makes a trip upstream to a certain point in 20 minutes; the trip takes 15 minutes. What is the current's speed? \n" ); document.write( "
Algebra.Com's Answer #421153 by josmiceli(19441)\"\" \"About 
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Let \"+c+\" = the speed of the current
\n" ); document.write( "\"+16+-+c+\" = the boat's speed going upstream
\n" ); document.write( "\"+16+%2B+c+\" = the boat's speed going downstream
\n" ); document.write( "given:
\n" ); document.write( "Going upstream:
\n" ); document.write( "(1) \"+d+=+%28+16+-+c+%29%2A%281%2F3%29+\"
\n" ); document.write( "Going downstream:
\n" ); document.write( "(2) \"+d+=+%28+16+%2B+c+%29%2A%281%2F4%29+\"
\n" ); document.write( "------------------------
\n" ); document.write( "Substitute (1) into (2)
\n" ); document.write( "\"+%28+16+-+c+%29%2A%281%2F3%29+=+%28+16+%2B+c+%29%2A%281%2F4%29+\"
\n" ); document.write( "Multiply both sides by \"+12+\"
\n" ); document.write( "\"+4%2A%28+16+-+c+%29+=+3%2A%28+16+%2B+c+%29+\"
\n" ); document.write( "\"+64+-+4c+=+48+%2B+3c+\"
\n" ); document.write( "\"+7c+=+16+\"
\n" ); document.write( "\"+c+=+16%2F7+\"
\n" ); document.write( "\"+c+=+2.286+\"
\n" ); document.write( "The current's speed is 2.286 mi/hr\r
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