# A runner covers a distance of 200 meters in 25 seconds. What is his speed in kilometer per hour?

Hello!

The speed is the distance travelled divided by the time spent. Here this is

(200 meters) / (25 seconds) = 8 m/s.

To express this in kilometers per second, let's express meters in kilometers and seconds in hours.

There are 1000 meters in one kilometer, therefore 1/1000 kilometers in one...

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Hello!

The speed is the distance travelled divided by the time spent. Here this is

(200 meters) / (25 seconds) = 8 m/s.

To express this in kilometers per second, let's express meters in kilometers and seconds in hours.

There are 1000 meters in one kilometer, therefore 1/1000 kilometers in one meter. There are 60 seconds in one minute and 60 minutes in one hour, so 60*60 = 3600 seconds in one hour. Or 1/3600 hours in one second.

Now, substitute this for 8 m/s:

8 meters/seconds = 8 (1/1000 kilometers) / (1/3600 hours) =

`8*(1/1000)/(1/3600)` km/h = `8*(3600/1000)` km/h = 8*3.6 km/h = 28.8 km/h.