Significant Digits

Question:

“what is the appropriate amount of significant figures for our calculations?”

Answer:

The significant figures in the answers depend on the significant figures in the measurements (i.e. the given values). When we are doing calculation, the rules below need to be followed:

"When multiplying or dividing measured quantities, round the answer to as many significant figures in the answer as there are in the measurement with the least number of significant figures; When adding or subtracting measured quantities, round the answer to the same number of decimal places as there are in the measurement with the least number of decimal places."

From Jingjie Teng

J. Mitchell Addition

• Intermediate calculations do NOT need to be rounded
• Conversion factors should be considered as exact unless you know they are accurate only to a limited number of figures
• e.g. 12” per foot is exact and has as many significant digits as needed.  Do not round to two digits because of this conversion factor
• Using Pi as 3.14 has only three significant digits.  Your answer should be rounded to three significant digits.