First, if you live in the Coventry area, I am performing and speaking at the lovely Albany Theatre on the 18th Match. Do come. Details here.
So, the puzzle. Please do NOT post your answer, but do say if you think you have solved the puzzle and how long it took. Solution on Monday.
You drive to your office at 20 mph and return by the same route at 30 mph. Discounting the time spent at the office, what was your average speed?
I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for the Kindle (UK here and USA here) and on the iBookstore (UK here in the USA here). You can try 101 of the puzzles for free here.