The key idea of number strategies at level 1 is that counting can be used to solve number problems.
At level 1, students see numbers as made up of ones, and to operate with numbers need to count the individual items. There are two main counting strategies that can be used to solve addition and subtraction problems:
- Counting from one. The most basic strategy for solving addition and subtraction problems is to count from one. For example, to solve 6 + 3, students could count a set of 6 objects, then count a set of 3 objects, then join the two together and count to find that there are 9 in the combined group.
- Counting on. Once students understand that the size of a set can be represented by the end number of its count, and have a firm grasp of number word sequence (see the key idea of Number Knowledge at level 1) they need to realise that when two quantities are joined, counting can begin from one of the quantities (instead of from one). They can then solve addition and subtraction problems by counting on or back from a starting number. For example, to solve 6 + 3 they recognise that 6 represents the first set, and count on from there “...7, 8, 9”.
Further information on number strategies can be found in the books supporting the Numeracy Development Projects.
This key idea develops from early experience with number during pre-school years.
This key idea is extended in the key idea of number strategies at level 2 where students are able to partition and combine numbers to solve simple addition and subtraction problems.