document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1201539>Question 1201539</A>: <I><SPAN STYLE=\"word-break: break-all;\"> <BR>\n" );
document.write( "A boat takes 12 hours to cover (D+30) km in upstream and it takes 8 hours to cover D km in downstream. If speed of stream is 4<BR>\n" );
document.write( "km/hr, then find the time (in hours) taken by boat to cover (D-64) km in upstream. </SPAN>\n" );
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document.write( "Let x be the speed of the boat in still water in km/hr. Then a single equation to set up the problem says that the distance covered in 12 hours at a speed of (x-4) km/hr is 30 km more than the distance covered in 8 hours at a speed of (x+4) km/hr:<br><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12%28x-4%29=8%28x%2B4%29%2B30 ALIGN=MIDDLE  ALT=\"12%28x-4%29=8%28x%2B4%29%2B30\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12x-48=8x%2B62 ALIGN=MIDDLE  ALT=\"12x-48=8x%2B62\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=4x=110 ALIGN=MIDDLE  ALT=\"4x=110\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x=27.5 ALIGN=MIDDLE  ALT=\"x=27.5\"   DISABLED_style= \"max-width:90%; height:auto;\" ><br><BR>\n" );
document.write( "The boat speed in still water is 27.5 km/hr<br><BR>\n" );
document.write( "The distance D is the distance covered in 8 hours at a rate of (x+4) km/hr: D = 8(31.5) = 252<br><BR>\n" );
document.write( "The time required to cover a distance of D-64 = 188 km at a rate of (x-4) = 23.5km/hr is<br><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=188%2F23.5=376%2F47=8 ALIGN=MIDDLE  ALT=\"188%2F23.5=376%2F47=8\"   DISABLED_style= \"max-width:90%; height:auto;\" ><br><BR>\n" );
document.write( "ANSWER: 8 hours<br><BR>\n" );
document.write( " </SPAN>\n" );
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