Question

If the speed of a car is increased by 10km/hour it takes 18minutes less to cover a distance of 36km then find the speed of the car

Answer 1

let speed be x

so,if speed is x+10 then it takes 18 minutes less

so, 36/x-36/x+10=18/60

36x+360-36x/x^2-10x=3/10

3600=3x^2-30x

1200=x^2-10x

x^2-10x-1200=0

x^2+30x-40x-1200=0

x(x+30)-40(x+30)=0

x=-30 or 40

as speed cannot be negative,

x=40

the original speed of car is 40 kmph