document.write( "Question 567816: the train covers 90km in uniform speed.if speed is raised 15km/hr then train covers distance in half hour less.find the original speed. \n" ); document.write( "

Algebra.Com's Answer #366736 by mananth(16949) $\"\"$ $\"About$

You can put this solution on YOUR website!
let speed be x km/h\r
\n" ); document.write( "\n" ); document.write( "increase by 15
\n" ); document.write( "=x+15\r
\n" ); document.write( "\n" ); document.write( "original time - time with increased speed = 1/2 hour\r
\n" ); document.write( "\n" ); document.write( "d=90 km\r
\n" ); document.write( "\n" ); document.write( "d/r = t\r
\n" ); document.write( "\n" ); document.write( "90/x-(90/(x+15)=1/2\r
\n" ); document.write( "\n" ); document.write( "multiply the equation by 2x(x+15) to eliminate the denominator
\n" ); document.write( "180(x+15)-180x=x(x+15)\r
\n" ); document.write( "\n" ); document.write( "180x+2700-180x=x^2+15x\r
\n" ); document.write( "\n" ); document.write( "90x cancels off\r
\n" ); document.write( "\n" ); document.write( "x^2+15x-2700=0\r
\n" ); document.write( "\n" ); document.write( "x^2+60x-45x-2700=0\r
\n" ); document.write( "\n" ); document.write( "x(x+60)-45(x+60)=0\r
\n" ); document.write( "\n" ); document.write( "(x+60)(x-45)=0\r
\n" ); document.write( "\n" ); document.write( "x= 45 km/h the original speed. Ignore negative value\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "

\n" );