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Page last updated at 10:57 GMT, Friday, 18 June 2010 11:57 UK

Taking maths to the street

By Ruth Alexander

There is a new breed of performer coming to a street near you - the maths busker. Think mathematicians-turned-entertainers. And they are recruiting. Would a BBC reporter with a rusty GCSE knowledge of the subject make the grade?

Ruth Alexander
Ruth Alexander takes her maths 'expertise' to Manchester city centre

"Maths axiom number one," trainer Matt Parker wrote on the whiteboard, "Maths busking is busking. We're not going out and doing a maths lesson on the street; we're not going out to lecture."

For the other trainees in the room at the University of Greenwich - mostly maths professors, teachers and students - this news was perhaps a little discomforting.

For me, it was a good job. Although the second principle of maths busking is more unnerving for me: maths is the gimmick.

Any performance was inescapably going to have to involve me wowing people with my maths.

Lecture over, we split into groups to learn some tricks to perform.

After what felt like not long enough at all, it was time for the debut performance.

Maths busking is basically a cross between magic and maths - the busker performs a seemingly blinding trick to an appreciative crowd. Behind it all is not sleight of hand or a secret compartment, but pure and (relatively) simple maths.

Ruth Alexander reports on maths busking for More or Less on BBC Radio 4, at 1330 on Fridays

My debut performance trick went like this:

- I picked a fellow trainee busker and stuck several pieces of sticky paper - one of which had a £20 note attached to it - all over him

- I then challenged someone else to play me for that £20

- The rules are simple - my opponent and I can take it in turns to pick pieces of paper off our human noticeboard. But neither of us can take off more than three pieces in one go

- The piece with the £20 on it must be the last to be picked off

To be in total control, I invite my opponent to go first - I just need to make sure there is always an even number of pieces of papers left - at least four - when it is his go.

Easy, really.

But, within seconds, I was beaten. Much to the amusement of the rest of the room.

I was so bad, our trainer Mr Parker seemed almost impressed. But he had some words of comfort - mastering the trick, he said, is not just about being able to count to four.

Multiples of four

"The underlying logic is all about patterns. It's a concept of maths called induction," he said.

"Once you've worked out how one bit works, you can add another bit on. So with that game, if you can do it with four, you can do it with eight, if you can do it with eight, you can do it with twelve."

Ruth and cohort busking
The yellow hoodies with 'Maths' were perhaps not the best uniform

Which helped me understand where I had gone wrong before.

Whereas I had had no idea how many pieces of paper I had pinned to my human noticeboard, the trick to the game, I realised, is to play with eight pieces of paper, or 12 or any other multiple of four. And to make sure four pieces of paper are taken off in each round.

So, if my opponent takes one piece, I should take three; if he takes two, I take two; if he takes three, I take one.

Shrugging off my comprehensive defeat, I agreed to join the maths buskers for a performance they had planned for the following week in Manchester city centre.

The other buskers taking part had all performed before - but only at science fairs and museums. I suspected that impressing shoppers in Manchester's Market Street with mathematical wonders would be a challenge for them too.

Odd one out

"No one has ever seen this before!" On the day, Dr Sara Santos from the Royal Institution of Great Britain, who was leading a team of four of us, was excited.

The public, less so.

Beaten by a young boy, in front of a sizeable crowd - the first lesson of maths busking - never underestimate your public

The buskers had imagined we would be performing to a crowd, but after 10 minutes of trying to attract people's attention, PhD student Katie Steckles was disheartened.

"This is really hard," she said. "People are just not up for maths."

We began to wonder about the wisdom of a decision to wear bright yellow hooded tops with the word "maths" emblazoned across the front.

But before long a couple of teenage boys, Ainsley and Perry, wandered over to take a closer look.

The buskers pounced on them.

Showing them five cards with numbers printed on them, Dr Santos asked them to say which cards their birthday was printed on.

One, two, three and four, Ainsley said.

"Your birthday is on the 30th," Dr Santos pronounced, correctly. The boys were amazed.

That is the power of binary numbers for you. (Want to know how it's done? See internet links, right)

Emboldened, I decided to have a go at performing my little number.

Real money

Instead of bits of sticky paper, I used pegs instead. Eight of them. And instead of a fake £20, I put a real one on the line. I had been practising.

Much to the disappointment of a number of passers-by.

It proved a popular game throughout the afternoon, and it really felt pretty good to have impressed some people with maths.

Until, that is, a young schoolboy called Joe came along. He had been observing my game, and had realised that I was winning because I was making sure my opponent always started the game. He insisted that to play him, I had to start first.

The maths buskers had warned me about this happening. The strategy in that case, they said, was to have nine pegs, not eight. And to take off the one extra peg with my first go.

So, I went first. And took off not one, but two pegs.

Oh dear.

Beaten by a young boy, in front of a sizeable crowd.

The first lesson of maths busking - never underestimate your public.

Brilliant mathematicians come in all shapes and sizes, and they are not always easy to spot.

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