The formula to use to calculate how fast a person is running is...
| SPEED = | DISTANCE |
| TIME |
If you want to know how long it will take a runner to cover a certain distance at a particular speed use...
| TIME TAKEN = | DISTANCE |
| SPEED |
If you want to know how far a runner will go in a certain time when running at a particular speed use...
| DISTANCE = | SPEED | x | TIME |