Number · Rounding & bounds
Chapter 1 · 3
The idea
Rounding and significant figures
Why significant figures count information rather than decimal places, why the count starts at the first non-zero digit, and why place value must survive the rounding.
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Number · Rounding & bounds
Rounding and significant figures
Why significant figures count information rather than decimal places, why the count starts at the first non-zero digit, and why place value must survive the rounding.
Why it works
Detail measured from where the number starts
Ask two students to round "to 2" and you can get from one and from the other — both followed a rule, but only one kept any information. The difference is which start line you measure from. Rounding answers one question: how much detail is worth keeping? Decimal places measure detail from the decimal point; significant figures measure it from where the number actually starts — the first non-zero digit.Keep reading — free
The rest of the explanation, plus 2 worked examples you step through move by move.
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