Final answer:
The mean concentration of a red blood cell is approximately 1.74%.
Step-by-step explanation:
The mean concentration of a red blood cell can be calculated by dividing the average volume of a red blood cell by the average volume of blood in an adult.
Let's assume the average volume of blood in an adult is 5 liters (5000 milliliters).
Since the average volume of a red blood cell is 87, the mean concentration would be:
(87 / 5000) * 100% = 1.74%
Therefore, the mean concentration of a red blood cell is approximately 1.74%.