In Kindergarten, children informally investigate joining groups to add (Early Counting and Grouping 13) and taking away from a group (Early Counting and Grouping 14), using counters. In Year 1, children begin to formally investigate joining groups to add, using the addition symbol (+) when they are ready to explain what it means. They explain that adding is starting with more than 1 group, and joining groups together, and taking away from a groups to subtract, using the subtraction symbol (-) when they are ready to explain what it means. They explain that subtraction is starting with 1 group, and taking a group away. Children use their number sense to identify which number they could make a group of, that would give them enough to take away the other number. (Addition and Subtraction 3).
Children then investigate adding and subtracting counting by ones on a number line, using the understanding they developed about numbers lines (Addition and Subtraction 1, Addition and Subtraction 2).
As children are investigating adding and subtracting counting by 1s, they also investigate place value concepts of friends of 10 (Place Value 6), partitioning single-digit and teen numbers (Place Value 8), and place value of teen numbers (Place Value 7). This will enable them to apply this understanding, to add and subtract single-digit numbers using place value concepts when they are ready.