Addition & Subtraction

In 1st grade the focus was on developing strategies for adding and subtracting within 20. These strategies include:

~ counting on or back

~ doubles and doubles plus or minus one

~ making a ten

In 2nd grade, students will add on to the strategies they learned in first grade and extend them to two and three digit numbers. Students will use the open number line as a tool to show their thinking.

The open number line is a tool used to show thinking as students decompose numbers in ways that make sense to them. Sometimes students look to make "friendly jumps" (by 10 or 20, etc) and sometimes students look to land on "friendly numbers" (40, 50, etc).

Agreements for the open number line:

~ arrows on both ends of the number line

~ greater values on the right

~ the starting number and the numbers landed on are labeled below the number line

~ use arrows to indicate addition or subtraction rather than the +, - symbols

~ label the amount on top of the hop (hops of 10 will be larger than hops of 1)