Question

a passenger train takes 2 hours 30 minutes more than an express train for a journey of 600km .the speed of the express train is 8km/h than the passenger train . Find the speed of the passenger train

Answer 1

Let x be the speed of the passenger train,

then x+8 is the speed of the express train.

Time spent by passenger train was $600/x$ and time for the express train was 600/(x+8).

$600/x -600/(x+8)= 2.5$

$600/x-600/(x+8)-2.5=0$

$(600(x+8)-600x-2.5x(x+8))/(x(x+8))=0$

$600x+4800-600x-2.5x^2-20x=0$

$-2.5x^2-20x+4800=0$

$x^2+8x-1920=0$

$D=8^2+4*1*1920=64+7680=7744$

$x1=(-8+88)/2=40$

$x2=(-8-88)/2=-48$

Choose the positive value, hence the speed of the passenger train was 40 km/h.