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 Question from mannal, a student: what negative integers do we use in the real world? like -30 temperature?

Hi Mannal,

Temperature is an obvious example of the use of negative numbers. (I'm going to talk about negative numbers in general rather than just negative integers.)

Another example is elevation. Elevation of points on the Earth are measured in metres above sea level. According to Wikipedia the surface of the Dead Sea is 420 metres below sea level so its elevation is -420 metres.

A shopkeeper calculates her monthly profit by subtracting her costs from the money she obtains from sales. If in some month her costs exceed her sales then she loses money and her profit (sales - costs) is negative.

If you are writing a computer program for a game and you need to put a character on the screen then the position of the character is relative to the upper left corner of the screen. It is so many millimeters to the right of this corner and so many millimeters down. If the character runs across the screen then its speed is in millimeters per second. If the character moves from left to right the speed is positive but if it moves from right to left its speed is negative.

I hope this helps,
Penny

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