DR MATHS.

DEAR Dr Maths, Having heard on the news recently that someone was incorrectly charged $23 quadrillion on their credit card, I wondered what is the name of the largest number? Derek, via e-mail $23,000,000,000,000,000 is a big error, but not the biggest name for a number. The table below shows the first few symbols, values and names for numbers. To find the value of a named number from one million take the prefix of the name, such as bi or two in billion, quad or four in quadrillion, octodec or 18 in octodecillion, etc, and add one to it.

Then multiply that result by three. For example, in a quadrillion the prefix is quad, meaning four. Adding one to it gives five. Now multiply five by three to give 15, which is the number of zeros you need to write.

Nicolas Chuquet, a French mathematician who lived in the 15th Century, is credited as the inventor of the modern names for large numbers. His book, Triparty en la Science des Nombres, shows a huge number divided into groups of six digits. He states that the groups can be called "million, the second mark billion, the third mark trillion, the fourth quad-rillionthe fifth quintillion, the sixth sexilion, the seventh septillion, the eighth octillion, the ninth nonillion and so on with others as far as you wish to go".

The Chuquet system for the naming of numbers goes on into larger and larger numbers, yet there is a special word for the name of a BIG number and that is called the Googol. This is defined as a number one followed by 100 zeroes and it was invented more for fun than for use. The story goes that in 1938 the mathematician Edward Kasner asked his nephew, who was then eight-years-old, what name he would give to a really large number, and "googol" was his response! Here is a puzzle for you to try: If you take one septillion from one octillion, how much do you have left? The first correct answer will win a copy of the book More Mathematical Curiosities, published by Tarquin. Well done to Joshua Glencorse, from Newcastle, who correctly worked out that in the pebble game the first player can always win if on his first move he takes two pebbles.

Do you have a maths question or problem? Write to Dr Maths, Evening Chronicle, Groat Market, Newcastle, NE1 1ED, or e-mail [e-mail]