If a boy takes as much time in running 10 m as a car

If a boy takes as much time in running 10 m as a car takes in covering 25 m, the distance covered by the boy during the time the car covers 1 km, is ?

Let distance covered by boy is Y.
Then, 25 : 10 : : 1000 : Y
⇒ Y = (10 x 1000)/25 = 400 m