Express your answers to problems in this section to the correct number of significant figures and proper units. (a) A person’s blood pressure is measured to be 120 ± 2 mm Hg . What is its percent uncertainty? (b) Assuming the same percent uncertainty, what is the uncertainty in a blood pressure measurement of 80 mm Hg ?

Solution 20PE: Step 1 of 4 (a) The formula to find the percent uncertainty is, p % uncertainty = p × 100 Here pis the uncertainty in blood pressure, is the pressure. Comment Step 2 of 4 The range of a person’s blood pressure is given as 120 ± 2mm Hg. Substitute 2mm Hg for pand for . 120mm Hg for P Therefore, 2mm Hg % uncertainty = (120 nn Hg× 100 = 2% Hence, the percent uncertainty is . Comment