### Negative number

There are many methods to avoid the use of **negative numbers**.

##### Times

You always write a year as a positive number, even if it was before the year zero. The old Greek Archimedes lived from ca. 287 - 212 BC. To avoid writing negative years, the addition Before Christ is used. You may write

from −287 till −212

but that looks so unfriendly. If someone was born in 12 BC and died in 64 AD, you calculate his age as

12 + 64 = 76

##### Temperatures

In weather forecasts you talk about 7° below zero when it freezes. If it gets two degrees colder, you can calculate

−7° − 2° = 9° below zero

That is a rather strange method, but we are used to it. If it gets three degrees warmer, you calculate

−9° + 3° = 6° below zero

If the temperature rises even further, with ten degrees, than you can calculate

−6° + 10° = 4° above zero

Fortunately, most people do that correct.