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Round up, then correct

Mental mathMedium

A fill list has rows, each carrying shares. Find the total share count without writing anything down.

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A whole number, a decimal, a fraction like 3/8 or a percent.

Hint

Replace by a round number and fix the error afterwards.

Solution
  1. Use , so .
  2. Compute .
  3. Compute .
  4. Subtract: .

Answer: