Question

A train travels 360km at a uniform speed had been 5km/h more, it would have taken 1 hour less for the same journey. Find the speed of the train

Answer 1

Answer:

Let the speed of the train originally be = x

Let the new speed = x+5

s=d/t

t=d/s

=>1= 360/x-360/x+5

=>1=360(1/x-1/x+5)

=>1=360($5/x^{2} +5x$)

=>$x^{2} + 5x = 360(5)$

=>$x^{2} +5x  -1800 = 0$

=>$x^{2} +45x -40x-1800=0$

=>$x(x+45)  -40(x+45) = 0$

=>x=40 or x= -45                

As speed of a object cannot be negative........

Hence original speed is 40km/hr