On October 30, 2018 at 10:35, highfigh said...
MAH is short for 'Miles In An Hour', which would be correct since either (MPH r MIAH) expresses the average speed.
Relaying this for a friend.
MAH is not short for 'Miles In An Hour.' You left out an initial. You show that yourself when you write 'MPH r MIAH.'
Plus, you ignore the meaning of 'per.' It is "for each" when used to express a rate. Since speed is a rate, that meaning applies here.
21 miles in an hour means that while an hour has elapsed, you have traveled 21 miles. That is, this means that an hour has elapsed and 21 miles have been traveled.
However, a speed of 21 miles per hour does not have those implications. You can travel 21 miles per hour for ten seconds or three days, but you cannot travel 21 miles in an hour for anything more than an hour. For more time, it would be, for instance, 42 miles in two hours.
