Games: numbers

Today is 11 December.

Eleven is a splendid number for books. If you take the ISBN of any book,for example 1 86066112 2, which is the ISBN of The Book of Numbers by William Hartston (Richard Cohen Books, pounds 9.99), then multiply the first digit by 10, the second by 9, and so on, adding up the answers as you go along (for the number above we get: 10+72+48+0+36+30+4+3+4+2 = 209) the answer will always be divisible by 11. This gives computers a simple check for ISBN errors.

Eleven is also the number of:

airports in Albania (though only five have paved runways);

cups of coffee drunk daily per capita in Sweden;

riots at horse races in the United States between 1960 and 1972;

ounces in weight the average person loses overnight;

golden hamster babies in the average litter;

recorded accidents in UK homes in 1994 involving drinking-straws.