The mass of potassium in a one cup serving of this cereal is determined to be 172 mg show a numerical setup for calculating the percent error for the mass of potassium to this serving.

[(172 - 170)mg/170 mg]*100% = 2*100%/170 = 1.18%

Explanation:

Generally percent error is calculated by dividing the error by the actual value of the variable at standard conditions. In the problem above, the acceptable or actual mass of potassium in a cup of the cereal is 170 mg and the estimated mass of potassium in a cup of the cereal is 172 mg. Therefore, the percent error = [(172 - 170)mg/170 mg]*100% = 2*100%/170 = 1.18%

there are two significant figures.