A car travels a distance of 840 km at uniform speed. If the speed of the car is 10 km/hr more. It takes two hours less to cover the same distance. The original speed of the car was?
Correct Answer: 60 km/hr .
Explanation:
Let the original speed be x km/hr.
Then, [ 840/x - 840/( x + 10) ] = 2
⇒ 840 (x + 10) - 840x = 2x (x+10)
⇒ x2 + 10x - 4200 = 0
⇒ (x + 70) (x - 60 ) = 0
∴ x = 60 km/hr.
