Numbers: An introduction to subtraction

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# 7 Subtracting decimals by lining them up

Subtracting whole numbers such as 52 from 375 is fairly straightforward. Subtracting decimal numbers such as 6.892 from 223.6 uses the same process but with one extra step – you have to line the decimal points up first.

Rather than arranging your two numbers so that they line up on the right-hand side, you need to line up the decimal points, regardless of how many numbers there are after the decimal point. In the example below, the top number has one number after the decimal point. It is said to have one decimal place. But the bottom number has three decimal places.

In any columns that are ‘missing’ numbers after the decimal point, assume that the missing number is zero, like this.

Now do the subtraction, starting on the right as usual, and borrowing from the next column where necessary.

When you have finished the calculation, remember to put the decimal point into your answer below the line, in the same position as the two numbers you are subtracting.

So the above subtraction when it is completed, with all its borrowings shown and with all its decimal points lined up, looks like this.

Sub_1

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