Question

A traincovers a distance of 90km at a uniform speed .had thespeed been 15km/hr more if would have taken 30 minutes less for thejouney.find the orignal speed of the train

Answer 1

answer is 15 km per hr the solution is let speed be x and time taken is t for covering 90 km. x=d/t that equals to x=90/t but it is given that x+15=90/t-30 by solving we get that xt-30x+15t-450=90.We know that from x=90/t that xT=90 and further solving leads to a quadtric equation 2x*x+30x-90=0 by solving we get x=15 km per hr .It is the original speed.