A student was trying to determine a formula for changing speeds that are written in feet per second

A student was trying to determine a formula for changing speeds that are written in feet per second into miles per hour. If a sprinter runs at a speed of n feet per second, what is her speed in miles per hour?

3600 seconds per hour = 3600n feet per hour

5280 feet per mile so we have:

3600n feet per hour / 5280 feet per mile = 0.6818n feet per second