Standard(s):
[MA2019] (1) 3 : 3. Apply properties of operations as strategies to add and subtract.
Examples: If 8 + 3 = 11 is known, then 3 + 8 = 11 is also known (commutative property of addition).
To add 2 + 6 + 4, the second and third numbers can be added to make a ten, so 2 + 6 + 4 = 2 + 10 = 12 (associative property of addition).
When adding 0 to a number, the result is the same number (identity property of zero for addition).
[MA2019] (1) 6 : 6. Add and subtract within 20.
a. Demonstrate fluency with addition and subtraction facts with sums or differences to 10 by counting on.
b. Demonstrate fluency with addition and subtraction facts with sums or differences to 10 by making ten.
c. Demonstrate fluency with addition and subtraction facts with sums or differences to 10 by decomposing a number leading to a ten.
Example: 13 - 4 = 13 - 3 - 1 = 10 - 1 = 9
d. Demonstrate fluency with addition and subtraction facts with sums or differences to 10 by using the relationship between addition and subtraction.
Example: Knowing that 8 + 4 = 12, one knows 12 - 8 = 4.
e. Demonstrate fluency with addition and subtraction facts with sums or differences to 10 by creating equivalent but easier or known sums.
Example: adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13
