Question

A passenger train takes 3 hours less for a journey of 360 km, if its speed is increased by 10 km / hr from its usual speed. What is the usual speed?

Answer 1

Usual speed of train = 30 Km/hr

Step-by-step explanation:

Let the usual speed of train be x.

Given:

360/ (x + 10) = 360/x - 3  as time = distance / speed

360x = (x+10) (360-3x)

360x = 360x - 3x² + 3600 - 30x

3x² + 30x - 3600 = 0

Dividing by 3, we get: x² + 10x - 1200 = 0

x² + 40x - 30x - 1200 = 0

x (x + 40) -30 (x +40) = 0

(x - 30) (x +40) = 0

So x can be +30 or -40.

Since speed is not negative, x = 30 Km/hr.

Usual speed of train = 30 Km/hr