1.8 Adding and subtracting decimal numbers
By now you should be familiar with decimal numbers, the different ways in which they can be represented (written in full, or simplified by using an exponent), and understand that by moving the decimal point to the left or right of its original position you can change the value of a decimal number by various factors of ten. In this section, we're going to explore how to add and subtract decimal numbers without using a calculator.
We use addition and subtraction all the time in our daily lives (for example, when estimating if we've enough money to buy a round of drinks, or comparing prices whilst out shopping). However, addition and subtraction are skills that you need to master, because you cannot rely on there always being a calculator to hand. Although this may sound like a trivial task that anyone can do, surprisingly few people are confident in these two skills, especially when under pressure! (It has been estimated that in England there are 14.9 million people aged between 16-65 who lack the skills to pass a maths GCSE qualification (DfES, 2003).)