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How many significant figures are in the measurement 0.00450 m?

Three: 4, 5 and the final 0. The leading zeros only place the decimal point.

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  1. Six
  2. Three ✔
  3. Two

Why: Leading zeros are never significant. A trailing zero after the decimal point is significant, because someone measured it. So 0.00450 has 3 significant figures.

Huh, didn't know that: Writing 4.50 x 10^-3 m in scientific notation shows the three significant figures at a glance.

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Leading zeros arrived early, but they still did not count.
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References

Answer: Three. Leading zeros are never significant. A trailing zero after the decimal point is significant, because someone measured it. So 0.00450 has 3 significant figures.

  1. OpenStax Chemistry 2e: 1.5 Measurement Uncertainty, Accuracy, and Precision openstax.org/books/chemistry-2e/pages/1-5-measurement-uncertainty-accuracy-and-precision
    Leading zeros, however, are never significant
    Checked 2026-10-10.
  2. OpenStax Chemistry 2e: 1.5 Measurement Uncertainty, Accuracy, and Precision openstax.org/books/chemistry-2e/pages/1-5-measurement-uncertainty-accuracy-and-precision
    the result to the same number of digits as the number with the least number of significant figures
    Checked 2026-10-10.

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