document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=111165>Question 111165</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A boat can go 20 mi against a current in the same time that it can go 60 mi with the current. The current is 4 mph. Find the speed of the boat in still water. </SPAN>\n" );
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document.write( "Let the speed of the boat be x mph<BR>\n" );
document.write( "speed of the current = 4mph\r<BR>\n" );
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document.write( "so speed against the current = (x-4)mph<BR>\n" );
document.write( "Distance traveled against the current = 20 miles<BR>\n" );
document.write( "So time taken = distance/speed<BR>\n" );
document.write( "              = 20/(x-4)\r<BR>\n" );
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document.write( "Now speed with the current = (x+4)mph<BR>\n" );
document.write( "Distance traveled with the current = 60 miles<BR>\n" );
document.write( "So time taken = distance/speed<BR>\n" );
document.write( "              = 60/(x+4)\r<BR>\n" );
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document.write( "As the time taken is the same,\r<BR>\n" );
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document.write( "   20/(x-4) = 60/(x+4)\r<BR>\n" );
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document.write( "Multiplying both the sides by (x-4)(x+4),\r<BR>\n" );
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document.write( "20(x+4) = 60(x-4)\r<BR>\n" );
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document.write( "==> 20x + 80 = 60x - 240\r<BR>\n" );
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document.write( "==> 240 + 80 = 60x - 20x [ collecting the like terms to one side]\r<BR>\n" );
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document.write( "==> 320 = 40x<BR>\n" );
document.write( "==> 320/40 = x<BR>\n" );
document.write( "==> 8 = x\r<BR>\n" );
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document.write( "Thus the speed of the boat in still water = 8mph\r<BR>\n" );
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document.write( "Best of luck!!!<BR>\n" );
document.write( " </SPAN>\n" );
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