If the speed of a car is increased by 10km per hr,it takes 18 minutes less to cover a distance of 36 km . Find the speed of the car
Let speed of the car be x km/hr
So
36/x-36/(x+10) =18/60
=>120(x+10-x)=x^2+10x
=>x^2+10x-1200=0
=>x^2+40x-30x-1200=0
=>x(x+40)-30(x+40)=0
=>(x+40)(x-30)=0
hence x= 30km/hr
