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Topic
Addition & Subtraction
Question
Practice: compute 374 + 489 mentally.
Answer
863 — add 500, then subtract 11.
374 + 489 → 374 + 500 = 874 → 874 − 11 = 863.
This is a useful variant of compensation: rounding by 11 is still easy if the round number makes the main addition trivial.
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