Significant Digits and Rounding Numbers Rules for determining the number of Significant Digits 1. All non-zero digits are significant. 2. Zeros between significant digits are significant. 3. Zeros to the left of the first nonzero digit are not significant. 4. A zero that ends a number and is to the right of the decimal point is significant. 5. A zero that ends a number and is to the left of the decimal point is significant only if it was measured. Significant Figures during Calculations 1. When performing multiplication or division, the number with the least number of significant figures will limit the certainty of the result. 2. When performing addition or subtraction, the result will have the same number of decimal places as the number with the fewest decimal places. Rules for Rounding Numbers 1. If the digit removed is more than 5, increase the preceding number by 1. 2. If the digit removed is less than 5, the preceding number is unchanged. 3. If the digit removed is exactly 5, the preceding number increases by 1 if it is an odd number and is unchanged if it is an even number.