document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=915694>Question 915694</A>: <I><SPAN STYLE=\"word-break: break-all;\"> to qualify for a lifeguard training course, you have to swim for 500 yards using either the front crawl or the breaststroke.  You swim the front crawl at a rate of 45 yards per minute and the breaststroke at a rate of 35 yards per minute.  You take 13 minutes to swim 500 yards.  How much time did you spend swimming the front crawl? </SPAN>\n" );
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document.write( "Crawl rate = 45 yards/min<BR>\n" );
document.write( "Breaststroke = 35 yards/min<BR>\n" );
document.write( "Total min = 13\r<BR>\n" );
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document.write( "unknown t = crawl time\r<BR>\n" );
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document.write( "crawl time + breakstroke time = 13\r<BR>\n" );
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document.write( " (crawl time)*(crawl rate) + (breakstroke time)(breakstroke rate) = 500<BR>\n" );
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document.write( "fill in what you know: \r<BR>\n" );
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document.write( "   t * 45 + (13-t) * 35 = 500<BR>\n" );
document.write( "   45t + 455 -35t = 500<BR>\n" );
document.write( "     10t  =  45<BR>\n" );
document.write( "      t =  4.5 hours for the crawl </SPAN>\n" );
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