As part of the preparations for London MathFest, there was an event in Lewisham's shopping centre. One activity involved a sign inviting people to "fold the paper in half 15 times and win pound;1,000". Of course, it could have been pound;1 million, and 10 folds, for all the difference it would make, because it is impossible. On the table we had a pile of A3 paper, some explanatory sheets and a calculator. People would fold a sheet until, after about six or seven folds, they could not go on. "It's not fair, the paper's too small" they would say. We were ready for that: under the table there was a supply of A1 flip chart paper. When this was pulled out their eyes lit up. This time they would manage seven or eight folds. It certainly kept shoppers engrossed.
The student teacher running the activity pulled up the sheet and with a calculator showed people how to work out how thick the paper would be if they could fold it 15 times. It works out to roughly 3 metres thick, about the height of the room they were standing in.
Mahs Year 2000 installed a collection of activities outside the Learning Zone in the Millenium Dome. The most intriguing puzzle is the pentomino set. Players put five squares sides by side to make a shape called a pentomino. There are 12 different ways of doing this. They can fit into a rectangle eight squares by five squares, but that one is extremely difficult. Despite many attempts when no one else was around, I never managed it. It looks easy, but you get down to one last piece and the hole is the wrong shape.
I have only ever seen two people solve it, one who spent an hour trying. The other spent five minutes, his hands moving at high speed, methodically checking possibilities. When the last piece went in, as he knew it would, he gave a half smile and walked off.
London MathFest January13-28 at 22 shopping centres, 15 museums and galleries, and includes 10 new maths trails and the first London Mathemagical Fun Fair. Details: www.mathsyear2000.orgwhatson or call learndirect free on 0800 100 900