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Mathematics: Adding and subtracting with negative numbers

ADDING AND SUBTRACTING WITH NEGATIVE NUMBERS

In this module, you can study how to add and subtract integers.

 

This ten-minute video from Khan Academy uses the number line to help you visualise adding and subtracting negative numbers. It's a long video, but it's worth watching the whole thing.

 

This short video explains why subtracting a negative is the same thing as adding a positive.

 

Did you know?

You add and subtract with negative numbers in everyday life when you estimate changes in temperature and bank balances.

 

Examples

10  +  -5 = 5        This is the same as 10 - 5 = 5

-10  +  -5 = -15    This is the same as -10 - 5 = -15

In these last examples, two 'minus' signs are side by side.  In this case the two signs make a positive.

-10  -  -5 = -5       This is the same as -10 + 5 = -5

10  -  -5 = 15       This is the same as 10 + 5 = 15

 

Be careful when using a basic calculator for these types of questions.  You need to learn the rules first for adding & subtracting integers.

Ideally, use a calculator that has brackets and enter the equations like this:

(-10)  -  (-5)  = 


Study and practice

HOW TO USE A BASIC CALCULATOR

The video explains how to use basic calculator functions and provides examples.

 

0.00 min      addition (+), subtraction (-), multiply (x), divide (÷)

1.19 min      decimal point
2.43 min      C, CE and backspace
4.19 min      square, square root & fractions
6.17 min      percentage (%)

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