From A to Book Fair

Today I went to the London Book Fair. As usual it was pretty busy, and most people were moving from meeting to meeting or wandering around. Or queuing for food or drink.

Trying to move about efficiently with so many people getting in your way is pretty hard.

For todays puzzle, if you wanted to travel to five different stalls just once, how many possible combinations are there? And how does this increase with the more stalls you have to visit. Can you work out the formula for the number of possible routes you can take if you have to visit n stalls?