**The one-sentence summary**

**Mathematical ideas underpin everything in our lives, from the geometry of a 50p piece to how probability can help you win in a casino.**

### WHAT THE BOOK SAYS

- This is not strictly a business book. It contains dispatches from the wonderful world of mathematics.
- Mathematical ideas underpin just about everything in our lives: from the surprising geometry of a 50p piece to how probability can help you win in a casino.
*Dyscalculia*is the condition of number blindness, in which sufferers don’t ‘get’ numbers as fast as most of us (dyscalculics wouldn’t enjoy this book).- By contrast,
*lightning calculators*are people who can compute highly complex calculations at high speed without using a machine. - People have been arguing about number systems for years – some prefer ten as a base, others twelve, and so on. (Grocers are so named because of their preference for counting in twelves, which is divisible by 2, 3, 4, and 6, and a gross is 144 – a dozen dozen).
*Tessellation*is the technical term for covering an area so that no part is left uncovered – something that only regular polygons can do (there may be an example on your bathroom floor).- In India,
*Slumdog Millionaire*was released as*Slumdog Crorepati,*because they do not have the word million. Our 100,000 is their*lakh,*and is written with the comma in a different place: 1,00,000. Ten l*akh*is a million, and ten million is a*crore.* - The phrase
*‘lowest common denominator’*is often used to describe something basic or unsophisticated, but this misrepresents the maths since an LCD can be as high as 468. The*highest common factor*is better. The HCF of 13 is 1, and you can’t much lower than that.

### WHAT’S GOOD ABOUT IT

- In 1972 the fist HP calculator killed off the slide rule – it cost £365, about half the salary of a junior engineer.
- Popular obsessions with numerical teasers continue unabated – sudoku, Rubik’s cube, and the Fifteen puzzle, which has one square missing in a frame and you have to get them in the right order.
- The
*Fibonacci sequence*is recurrent, with each term generated by the values of the previous terms: 1, 2,3, 5, 8, 13, describes the breeding of pairs of rabbits, and pretty much all cell division in nature. - You can’t square a circle – that is to measure the circumference with total accuracy – because the true number is beyond the realm of finite algebra.
- The 50p and 20p pieces are design classics – curvaceous heptagons.

### WHAT YOU HAVE TO WATCH

- It has some very technical moments that are so complex you just have to move on.