Question

A car travelled a distance of 840 km at a uniform speed. if the speed of the car were 10 km/hr more, then it would have taken two hours less to cover the same distance. the original speed of the car was

Answer 1

Distance = 840 km
let original speed = x km/h
New speed = x +10 km/h

ATQ

840/x - 840/(x+10) = 2 ( time equation)

(x +10 -x )/x*(x+10) = 2/840

10/(x^2 +10x) = 1/420

x^2 + 10x - 4200 = 0

x^2 +70x -60x -4200= 0

x(x + 70) -60(x + 70)=0
(x +70)(x-60) = 0
x = 60 km/hr as it can't be negative.