Basic Decimal Skills Needed to Pass Numeracy Tests - dummies

Basic Decimal Skills Needed to Pass Numeracy Tests

By Colin Beveridge

You need to know how to work with decimals to pass most numeracy tests. When you’re adding or taking away decimals, the way you lay out your working becomes even more important than normal. If you get your dots in the wrong place, you’ll end up adding the wrong things together and get a wildly wrong answer!

Adding and taking away decimals

Adding and taking away decimal numbers works just the same as adding and taking away normal numbers. The one thing to take care of first is if you have different numbers of digits after the decimal point, add in enough zeros at the end of the shorter number to make them the same length.


After that, you can just use the same methods as you normally use for adding and taking away numbers.

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Multiplying and dividing decimal numbers

In a numeracy test, it’s really unlikely that you’d be asked to do anything trickier than multiplying or dividing a decimal number by a whole number.

The same methods you use for multiplying and dividing normal numbers work just the same as for decimals.

As with adding and taking away, you need to be a bit careful about where the dots go, but follow these steps, and you’ll be fine to work out sums such as 5.67 x 3 and 7.413 / 7:

  1. Count how many spaces from the end of the decimal number the dot is. Write this down and put a circle around it, you’ll need it later.

    For the first example, that would be 2; for the second, it would be 3.

  2. Forget about the dot and do the sum as normal. 567 x 3 = 1702 and 7413 / 7 = 159.

  3. Put a dot at the end of it.

  4. Move the dot left by the number of spaces you wrote down in Step 1.

    If you go off before the start of the number, it’s ok – just put as many extra zeros at the beginning as you need. In the first example, you need to move the dot back two spaces to make it 17.02; in the second, you move it back three spaces to make 0.159.