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When adding and subtracting numbers it's important to be consistent with positive and negative values. Remember that two plus signs or two minus signs make a positive. One plus and one minus make a negative.

In the column method of addition and subtraction, numbers are written so their place values line up vertically forming columns for ones, tens, hundreds, thousands etc.

Place value is the value of each digit in a number, for example ones, tens or hundreds. Decimal place values include tenths, hundredths and thousandths. The value of a digit goes up by ten as it moves to the left.

When adding and subtracting decimals it is important to keep place values consistent. Remember to be careful when using positive and negative values.

Both positive and negative numbers can be multiplied and divided using rules. Two signs the same gives a positive answer. Two different signs give a negative answer. More difficult multiplication can be carried out using the grid or column method. Division can be worked out using short or long division.

Multiplying a decimal by a whole number uses the same method as multiplying two whole numbers. When multiplying by 10, 100 or 1000 you need to move each digit the correct number of places to the left.

Dividing decimals by whole numbers works the same way as dividing whole numbers except, just like addition and subtraction of decimals, the decimal point must be kept in line. When dividing by 10, 100 or 1000, remember to move all digits the correct number of places to the right.