Addition and Subtraction to 20
Warm-up
Doubles challenge: teacher says a number 1-10 and students say the double. Then near-doubles: 6+7. Who can explain? I know 6+6=12, so 6+7 is one more: 13. This warm-up activates the doubles strategy before the lesson.
Explore
Stations: (1) Doubles and near-doubles with linking cubes: build double towers, then add one more. (2) Making-10 with ten-frames. (3) Fact families: given one fact, write the other three. Rotate after 5 minutes. Circulate and ask students to explain their reasoning.
Consolidate
Practice
Students complete a mixed set of addition and subtraction problems to 20, writing their strategy beside each answer. Exit ticket: 15-7. Students write the answer and the related addition fact they used.
Exit ticket
Students complete a mixed set of addition and subtraction problems to 20, writing their strategy beside each answer. Exit ticket: 15-7. Students write the answer and the related addition fact they used.
I know 7+7=14. 8 is one more than 7, so 7+8 = 14+1 = 15. This is faster and more reliable than counting on. Draw two towers of 7 with one extra cube to show the near-double relationship.
Use a fact family triangle: write 5, 8, and 13 at the three corners. Cover one number. We know 5 and 8. What is hiding? Cover a different corner. 13 and 5 are together. What is missing? The triangle makes all four facts visible from one structure.