here we have to calculate the time taken by a Racehorse to cover a distance of 400 metre
as per the question the speed of the horse is 20 m/s
hence we have speed[V] = 20 m/s
the distance covered [S]=400 m
the relation between distance,time and the speed is given as
![distance= speed *time](https://img.qammunity.org/2019/formulas/physics/middle-school/9094iquckjlxkqvg7glhpfjc77z9jsp4xo.png)
![S= v*t](https://img.qammunity.org/2019/formulas/physics/middle-school/7xdca37cmzuhn61uut43wuh6ll03tmmcif.png)
=
![(400m)/(20 m/s)](https://img.qammunity.org/2019/formulas/physics/middle-school/psb5tnym9ya4n412uwsfsuptidyghgquu0.png)
=20 second
hence the time taken by the horse is 20 second [ans]