Question

A bus covers a distance of 90 km at a uniform speed. Had the speed been 15 km/hour more it would have taken 30 minutes less for the journey. Find the original speed of the bus.

Answer 1

Answer:

45 km/hr

Step-by-step explanation:

let original speed be x

90/x - 90/(x + 15) = 30/60

90 [ 1/x - 1/x+15] = 1/2

2 ×90 ×15 = x^2 + 15x

x^2 + 15x - 2700 = 0

x^2 + 60x - 45x - 2700 = 0

x(x + 60) - 45( x + 60) = 0

x = - 60 , 45

speed can't be taken as - ve so

original speed = x = 45 km/hr