Marathon runner velocity problem

[Allura]

1. Consider a marathon of 42.195 kilometers. In order to attain the qualifying time of 3 hours and 15 minutes to enter the race, a runner would need to run at an average velocity (in m/s) of



2. I thought this would be average speed = distance traveled/time interval spent traveling



3. Since they wanted it in terms of m/s, I divided 42.195 by 1000. Then to get seconds, I converted 3 hr and 15 mins to 11700 seconds, which gives 3.6E-6.

But apparently its wrong. Help?

 

[iamalexalright]

Why did you divide by 1000?

 

[Allura]

To go from kilometers to meters

 

[iamalexalright]

You are not canceling units correctly:

$$1 km * 1000 \frac{m}{km} = 1000 m$$

 

[Allura]

Ohhh, the right is answer is 3.6 then. Thanks! That makes more sense.