GRADE 1 · ALBERTAOUTCOME AB-G1-1N2
L3 · Thinking addition to subtract: inverse operations
Learning goal
“I can use a sum I know to find a difference.”
Undo — to go back to how things were.
Related — belonging to the same family of facts.
Check — use adding to test a subtraction.
Worked example
13 - 6. Think addition: 6 + ? = 13. 6 + 7 = 13, so the missing part is 7. 13 - 6 = 7. Say it plainly: addition and subtraction undo each other. A sum you know can answer a subtraction.
Check yourself — explain it
Addition helps with subtraction because...
Paired problem — example still visible
14 - 8: think 8 + 6 = 14. -> 6
Faded completion — last step is yours
"12 - 5: 5 + ___ = 12, so 12 - 5 = ___." -> 7; 7
Ready to practise?
8 scored questions with a 3-rung hint ladder. Mastery needs 7/8 plus both gate questions.