document.write( "Question 1167533: when a bicyclist is 20 km from her destination she realizes that she will be 10 minutes late unless she increases her speed by 10 km. What is her current speed \n" ); document.write( "

Algebra.Com's Answer #792134 by ikleyn(52812) $\"\"$ $\"About$

You can put this solution on YOUR website!
.
\n" ); document.write( "

\r\n" );
document.write( "\r\n" );
document.write( "The current speed = x  km/h.\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "The increased speed = (x+20)  km/h\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "The \"time\" equation is\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "     -  =   of an hour (which is 10 minutes).\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "Multiply both sides by 6x*(x+20).  You will get\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "    120*(x+20) - 120*x = x*(x+20)\r\n" );
document.write( "\r\n" );
document.write( "    120x + 2400 - 120x = x^2 + 20x\r\n" );
document.write( "\r\n" );
document.write( "    x^2 + 20x - 2400 = 0\r\n" );
document.write( "\r\n" );
document.write( "    (x+60)*(x-40) = 0\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "Of the two roots, -60 and 40, only positive is meaningful.\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "ANSWER.  The current speed is 40 km/h.\r\n" );
document.write( "

\r
\n" ); document.write( "\n" ); document.write( "Solved.\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "

\n" );