Question

The speed of a express train and speed of a ordinary train is less by 8 km/hr than espress train. If
express train takes two hours less than the ordinary train to cover distance of 480km. Find the speed
of both trains . ( Solve by quadratic method)

Answer 1

Let x be the speed of express train

speed of slower train = x-12

travel time = distance / speed

[240/(x-12)] -[240/x] =1

Least Common Divisor of the above fractions is

x(x-12)

240x - 240x + 2880=x2 - 12x

x2 -12x - 2880 = 0

(x+48)(x-60)=0

x = - 48 or x = 60

 

As speed cannot be negative, we discard the result x= -48.

Therefore, speed of the express train is 60 km/hr

(JUST SUBSITUTE THE VALUES 12 TO 8 AND 240 TO 480)