Question

A passenger train takes one hour less for a journey of 150km if its speed is increased by 5km/hr from its usual speed. Find the usual speed of the train.

Answer 1

Let the usual speed of train be x km/hr

Then, increased speed of the train = (x + 5)km/hr

Time taken by the train under usual speed speed to cover 150 km = hr

Time taken by the train under increased speed to cover 150km =hr

So, it is given that

$750=x^2+5x$

$x^2+5x-750=0$

$x^2+30x-25x-750=0$

$x(x+30)-25(x+30)$

$(x-25)(x+30)$

x = 25 or x = - 30

Since, the speed of the train can never be negative

Therefore, the usual speed of the train is x = 25km/hr