Answer:
Another poorly worded homework question. While you could answer what the mean hourly snowfall was between 4PM and 7PM, that’s not what the question asks. It asks simply what the mean hourly snowfall is. You know that there are a total of 11 cm of snowfall, but you don’t know the time frame over which it fell.
So the simplest form is really an equation. 11cm / (7PM - time the snow started)
