Åk 6–9
1.1 Introduction
Have you ever heard about numbers which are less than zero? You have probably come into contact with numbers less than zero before even if you haven’t really thought about it.

If you owe a person something or if it is very cold out, then you need to use numbers which are less than zero.  We usually call these negative numbers.  A negative number is a number which is less than zero.

There are many examples in daily life where we use negative numbers:

  • The most common example, which fits a country like Sweden, where we have cold winters, is the thermometer.  When it is cold it is usually negative degrees, temperatures which are lower than 0.

Foto: Fredrik Enander

  • The Mariana Trench in the Pacific Ocean is over 10,000 meters deep.  Sea level is normally called 0 meters, and the Meriana Trench lies 10,000 m under 0.  The world’s tallest mountain, Mount Everest, reaches 8,848 above sea level.

  • If you were to buy something expensive, you usually loan money from a bank and then owe the bank.  To have a debt or to owe money is usually written as a negative number.

  • If you called to another part of the world, you need to find out what the time is there and consider the time zone.  Moscow is 2 hours before Swedish time, and Lima is 6 hours after Swedish time.