# Term 2 2015 - Maths Stage 4 - Addition and Subtraction

Key Teaching Ideas:

Our number system is based on ten.

Basic fact knowledge can be used to add and subtract tens.

Numbers can be rearranged and combined to make ten.

Addition is associative, so addends can be re-grouped to solve a problem more efficiently.

Addition and subtraction problems can be solved by partitioning one of the numbers to go up or back through ten.

Subtraction problems can be solved by going back through ten, partitioning numbers rather than counting back.

Change unknown problems can be solved by using place-value knowledge of tens and ones or by partitioning through tens.

Subtraction can be used to solve difference problems in which two amounts are being compared.

Knowledge of doubles can be used to work out problems close to a double.

The equals sign represents balance.