Question

The speed of an express train is x km/hr and the speed of an ordinary train is $12Km/hr$ less than that of the express train. If the ordinary train takes one hour longer than the express train to cover a distance of $240$km, find the speed of the express train.

Answer 1

Let the time taken by express train to cover $240km$ be $yhr$ and speed be $xkm/hr$

$xy=240$

And $(x-12)(y+1)=240$

$⟹xy-12y-12+x=240⟹x=12y+12$

Since $xy=240⟹y(12y+12)=240⟹12(y+1)y=240⟹y=4$

$xy=240⟹4x=240⟹x=60$

Speed of the express train $=60km/hr$