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Rules governing significant figures Basic rules 1. Any non-zero digit is significant. 2. Zeros between non-zero digits are always significant. Example: 3,606 has 4 significant figures. 3. Zeros that indicate the decimal point are not significant. Example: 360,600 has 4 significant figures. 4. Zeros following a decimal are significant. Example: 3.60 has 3 significant figures but 3.6 has 2. 5. Zeros appearing before a non-zero digit are not significant. Example: 0.009 only has 1 significant figure. Addition and subtraction rule The number of significant figures in a sum or difference is equal to that of the least accurate measurement in the equation. The answer must contain the same number of decimal places as the least accurate measurement. Example: Without using significant figures: 606.02 – 65.3 = 540.72 Using significant figures: 540.7 Multiplication and division rule The number of significant figures in a product or quotient is equal to that of the least accurate measurement in the equation. The answer must contain the same number of significant figures as the least accurate measurement. Example: Without using significant figures: 606.02 × 63 = 38,179.26 Using significant figures: 38,000 (has only 2 significant figures)