You can put this solution on YOUR website! How do you convert 3 seconds per feet to miles per hour? This is from a handout-not from a textbook
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3 sec/ft is 1/3 ft/sec.
You can do all the numbers and get that 15 mph = 22 ft/sec.
--> 1 ft/sec = 15/22 mph
1/3 ft/sec = 5/22 mph