# A 22-inch Domino Pizza would be free

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Want an absolutely huge Domino Pizza for free? Just ask a teacher. When pizza meets physics it become theoretically possible to order a 22-inch Domino Pizza and pay nothing for it.

Reigate physics teacher Alby Reid has calculated that, as Domino pizzas cost less per square inch the bigger they get, if Domino made one 22 inches across it would be free.

#### Do the maths

The science boffin has used complex mathematical equations to plot the three domino pizza prices on a graph. Extending the line shows that – theoretically of course – if Domino stuck to its price to size structure, pizzas would drop to a zero price once Domino made one 22 inches.

He first produced a graph showing how as a pizza's diameter grows the actual size of the pizza in terms of square inches (the area) grows much faster. A 12-inch pizza is not twice the size of a six inch pizza but is actually four times as big. But it was when he came to the price that it got really complicated.

#### Domino prices

• Small (9.5 inches) £12.99
• Medium (11.5 inches) £14.99
• Large (13.5 inches) £16.99

Surrey science teacher Mr Reid, as he calls himself (well as his school kids call him), plotted those on a graph (new window). He then details a very complex calculation that produced a bell-shaped graph with the zero price being hit at both -128 inches and 22 inches.

With classic professorial understatement he writes: "Since a pizza with a diameter of negative 128 inches is clearly ridiculous, it's the free 22-inch pizza that is interesting."

Mr Reid's blog contain plenty of other fascinating scientific insights as he tries to interest his pupils (and ignorant people like us) in the technical side of the world around us. "If I write long, complicated post on nuclear power, it gets ignored, but a silly post about pizzas goes massive," he told AOL Money.

#### Good teaching

Pretty much everyone has lamented the poor teaching of maths in schools these days. The RSA has just produced a report claiming: "English maths education is not fit for purpose and is damaging the UK's competitiveness". It said: "Many students do not realise that mathematics is necessary for success."

But teachers such as Mr Reid stand out. "I'm a physics teacher. The blog is about things that interest me. I know some of my class look at it but I don't use it in formal teaching," he told AOL Money.

But what does Domino Pizza have to say about the free 22-inch pizza and Mr Reid's calculations? "We love this! It's great to see our pizzas being used in education. We're going to take a look into this theory but unfortunately we don't think we'll be giving away any free 22-inch pizzas anytime soon – for a start, they wouldn't fit in our hotbags."