A car travels 5 miles north and then 2 miles south in 1/4 hour. What was its average velocity?

12 mph north

Explanation:

Average velocity is displacement over time.

v = Δx / t

If we take north to be positive and south to be negative:

v = (5 mi - 2 mi) / ¼ hr

v = 12 mi/hr

v is positive, so it is in the north direction. Therefore, the average velocity is 12 mph north.