Mental strategies including estimation to add/subtract whole numbers up to 20
10 tutor-authored questions for this Ontario curriculum expectation, ordered easiest to hardest — every one with a full worked solution. Work through them free, no account needed.
Sample: the first question, solved
Add mentally: 8 + 5.
📘 Worked solution
✓13.
And one from the hard end
Estimate first, then find the exact answer: 12 + 7.
Solution shown after you try it in practice mode.
Work through all 10, easiest to hardest
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