Final answer:
Add the volumes 12.01 mL, 35.2 mL, and 6 mL to get 53.21 mL and round to the least number of decimal places, which is zero, resulting in a final answer of 53 mL.
Step-by-step explanation:
To perform the calculation with the correct number of significant figures, we add the values 12.01 mL, 35.2 mL, and 6 mL together. The least number of decimal places in the measurements provided is zero (as with 6 mL), which means our final answer should be rounded to the nearest whole number. Adding the volumes we get 12.01 mL + 35.2 mL + 6 mL = 53.21 mL. Since we must round to the nearest whole number due to the least precise measurement (6 mL), the correct final answer is 53 mL.