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How do you ensure an answer is not reported as more accurate than the real-world measurements you used for obtaining it?
Rules of significant digits should be used.
When calculating with real-world measurements, we need to be sure that answers are not reported as more accurate than the measurements themselves. To ensure that, we should follow the rules for significant digits in calculated measurements.
| Operation | Rule |
|---|---|
| Addition or Subtraction | The sum or difference must be rounded to the same place value as the last significant digit of the least precise measurement. |
| Multiplication or Division | The product or quotient must have no more significant digits than the least precise measurement. |
Let's use these rules in a real-life situation.
As a part of a school project, Samuel measured the dimensions of a basketball court. He also drew a diagram to show his results.
Let's calculate the perimeter of the court. P=28.73+15.2+28.73+15.2=87.86 m The least precise measurement is written to the nearest tenth. Thus, we should also write the perimeter corrected to the nearest tenth. 87.86 ≈ 87.9m The perimeter of the court is 87.9m. Let's now find the area of the court. A=28.73* 15.2=436.696m^2 The least precise measurement is given to three significant digits. Thus, we should also write the area correct to three significant digits. 436.696 ≈ 437 The area of the court is 437m^2.