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Estimating by rounding

Mathematics · Addition & Subtraction · meta

Estimate the answer to a calculation and use inverse operations to check answers; apply to increasingly large numbers using rounding and inverse reasoning

What mastery looks like

  • Round numbers to the nearest 10 or 100 to estimate a sum or difference before calculating
  • Use addition to check a subtraction answer, or vice versa
  • Identify when a calculated answer is unreasonable based on the estimate
  • Round numbers to estimate a sum or difference before calculating
  • Use addition to check a subtraction answer and vice versa
  • Identify an unreasonable answer by comparing to the estimate

Check your understanding

Before Estimating by rounding works out a calculation, can they make a sensible rough guess — and then check their answer using the opposite operation?