How many minutes can you spend on the swings before the warden comes round to lock up at 6pm? He is at the end of the park, averages three miles an hour walking pace, and has a dodgy leg which slows him down on the gravel. Then add the amount of time you can keep him talking if a) he's in a good mood and b) he's hungry. And if it's not maths, it's called Living in the real world.
