Question 159283
40 miles   5280 feet
-------- x ----------
 1 hour       1 mile
.
Notice the units cancel leaving:
(40*5280) feet/hour
211200 feet/hour
.
211200 feet/hour * 1hour/60minutes
= 3520 feet/minute
.
Finally,
3520 feet/minute * 1min/60secs
= 58.67 feet/sec
.
Conclusion:
40 mph is the same as 58.67 feet/sec