Question

A train covers a distance of $90$ km at a uniform speed. had the speed $15$ km/hr more ,it would have taken $30$ minutes less for the journey. Find the original speed of the train.

Answer 1

let $x$ km/hr be the original speed of the train

according to the question

$\frac{90}{x}-\frac{90}{x+15}=\frac{1}{2}$

$180x+2700-180x=x^2+15x$

$x^2+15x-2700=0$

solving the equation we have

$x=45$ and $x=-60$

Therefore the original speed of the train was $45$ km/hr.