Units & Conversion · 有效数字 · Updated 2026-10-25
What Is Significant Figures?
Definition
Significant figures express honest precision: multiply/divide → fewest sig figs; add/subtract → fewest decimal places. 1.5×2.345 = 3.5, not 3.5175.
Formula
Multiply/divide: fewest sig figs; add/subtract: fewest decimals
Worked Example
68.5kg / 1.72m gives BMI 23.2 (not 23.153) — the inputs only justify three sig figs.
Common Misconception
"More decimals mean more precision" - digits beyond input precision are meaningless false precision; "5 always rounds up" - statistics and engineering use round-half-to-even to curb accumulated bias.
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