When weighing a patient on a balance scale with weights set at 150 on the upper calibration bar and 21.5 on the lower bar, what is the total weight of the patient?

To determine the total weight of the patient using the balance scale, you add the values from both the upper and lower calibration bars. The upper calibration bar indicates a weight of 150 pounds, while the lower calibration bar shows an additional 21.5 pounds. To find the total, simply add these two values:

150 + 21.5 = 171.5 pounds.

This calculation confirms that the total weight of the patient is 171.5 pounds. The correct answer is indeed 171.5 pounds, which aligns with the choice indicating that as the total weight of the patient. The understanding of how to read and combine weights from both bars is essential for operating a balance scale correctly and accurately assessing a patient's weight.