A runner wants to run 11.6 km. She knows that her running pace is 8.1 miles per hour. How many minutes must she run?

Answer 1

speed = dist/time (as in miles/hr)
The sneaky part here is that everything is in different units. You want to end up with minutes. So, convert everything to miles and minutes

11.6 km * mi/1.6km = 7.2 mi

so, plug and chug:
speed = dist/time
8.1 = 7.2/t
t = 8/9 hr

But we want minutes = 66*8/9 = 53 1/3 min.

Answer 2

oops, that's 60*8/9