1.OA.4

Understand subtraction as an unknown-addend problem. For example, subtract 10 – 8 by finding the number that makes 10 when added to 8. Add and subtract within 20.

1.OA.5

Relate counting to addition and subtraction (e.g., by counting on 2 to add 2).

1.OA.6

Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on; making ten (e.g., 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 – 4 = 13 – 3 – 1 = 10 – 1 = 9); using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 – 8 = 4); and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13).

### Time Frame: 10-25 Minutes, depending on class

# Activity:

Students will be able to self-asses their own growth in this leveled worksheet. You can either enforce a time limit to see how much progress students make in the given time period, or you can time how long it takes each student to finish the activity.

Sample(Click to Enlarge)