Question

By increasing the speed of a bus by 10 km/hr , it takes one and a half hours less to cover a journey of 450km . Find the original speed of the bus

Answer 1

let the original speed be x

time = distance / speed

original speed = x

new speed = (x+10)

(450 / x) - (450 / (x+10)) = 3/2

(450(x+10) - 450x) / (x^2 + 10x) = 3/2

(450x + 4500 - 450x) / (x^2 + 10x) = 3/2

9000/3 = x^2 + 10x

x^2 + 10x -3000 = 0

after factorizing we get

x^2 + 60x -50x -3000 = 0

x (x+60) - 50 (x+60) = 0

x = 50, -60

ignoring negative value

we get x = 50 is the original speed