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Rules for rounding off numbers. If the digit to be dropped is greater than 5, the last retained digit is increased by one. For example, 12.6 is rounded to 13. If the digit to be dropped is less than 5, the last remaining digit is left as it is. For example, 12.4 is rounded to 12.
SIGNIFICANT FIGURES. The amount of approximation required in a number may be described in another way by saying how many significant figures are required. To find how many significant figures a number contains count all figures in the number except zeros at the beginning or end of the number.
Rounding is the process of reducing the number of significant digits in a number. This can help make it easier to remember and use. The result of rounding is a "shorter" number having fewer non-zero digits yet similar in magnitude.
• Significant figures: digits in the number that are reliable and absolutely necessary to indicate the quantity of something (Wikipedia). • Number of significant digits depends on the precision of the analytical method • More significant figures do not give more information on accuracy
There are three rules on determining how many significant figures are in a number: Non-zero digits are always significant. Any zeros between two significant digits are significant. A final zero or trailing zeros in the decimal portion ONLY are significant. Focus on these rules and learn them well.
Significant Figures and Rounding – Explanations and Examples Read pages 18-22 in your Lab Manual for a more thorough discussion of the meaning of significant figures and how it relates to accuracy, precision, and error.
Significant Figures: Fundamentals. Use these rules when recording measurements and rounding calculations in chemistry. When Recording a Measurement. Write all the digits you are sure of, plus the first digit that you must estimate in the measurement – the first doubtful digit (the first uncertain digit). Then stop.
