Significant Figures: Precision in Measurement
Sig figs report measurement precision. Non-zero digits always count. Leading zeros don't; trailing zeros in decimal do. Mult/Div: min sig figs; Add/Sub: min decimal places.
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12.5 ร 3.4 = 42.5 โ 43 (2 sig figs, from 3.4). 1.00 + 0.1 = 1.10 โ 1.1 (1 decimal place). 0.0034 has 2 sig figs. 1200 ambiguous: 1.2ร10ยณ or 4?
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Why: Scientists use sig figs to convey precision. 12.5 has 3 sig figs; 0.0012 has 2. Mult/Div: result has fewest sig figs. Add/Sub: fewest decimal places.
How: Count: non-zero digits always; zeros between count; leading zeros don't; trailing zeros in decimal do. Mult/Div: round to min(sig figs of operands). Add/Sub: round to min(decimal places).
Run the calculator when you are ready.
Enter Values
Digit Breakdown
Digit Classification
Significant vs Not
๐ Step-by-Step Breakdown
For educational and informational purposes only. Verify with a qualified professional.
๐งฎ Fascinating Math Facts
Mult/Div: result = min(sig figs)
โ Precision
Add/Sub: result = min(decimal places)
โ Precision
๐ Key Takeaways
- โข Non-zero digits (1โ9) are always significant
- โข Zeros between significant digits are significant (101 has 3 sig figs)
- โข Leading zeros are NOT significant (0.001 has 1 sig fig)
- โข Trailing zeros after decimal ARE significant (1.00 has 3 sig figs)
- โข Mult/Div: Result has same sig figs as operand with fewest
- โข Add/Sub: Result has same decimal places as operand with fewest
๐ก Did You Know?
๐ How to Count Sig Figs
- Identify the first non-zero digit from the left.
- Count all digits from that point, including zeros between non-zero digits.
- If there is a decimal point, count trailing zeros after the last non-zero digit.
- If no decimal point, trailing zeros are ambiguousโuse scientific notation.
๐ Worked Example: 0.00123
Step 1: Leading zeros (0.00) are NOT significant
Step 2: First significant digit is 1
Step 3: 1, 2, 3 are all significant. Result: 3 sig figs
โ ๏ธ Common Mistakes to Avoid
- Rounding too early: Keep extra digits during intermediate steps; round only the final result.
- Confusing decimal places with sig figs: Add/Sub use decimal places; Mult/Div use sig fig count.
- Ambiguous trailing zeros: Write 1.00ร10ยฒ instead of 100 when you mean 3 sig figs.
โ FAQ
What are significant figures?
Digits that carry meaning about precision. They indicate how precisely a measurement was made.
Why are trailing zeros ambiguous?
In 100, we cannot tell if zeros were measured (3 sig figs) or placeholders (1 sig fig). Use scientific notation for clarity.
How do I round to sig figs?
Identify the first significant digit, count N digits, then round. 0.001234 to 2 sig figs = 0.0012.
๐ Summary
Significant figures communicate measurement precision. Follow NIST/ACS conventions. Use scientific notation for ambiguous cases.
โ ๏ธ Disclaimer: Sig fig rules may vary by discipline. This calculator follows NIST/ACS conventions.
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