Final answer:
Madison should use the exponent format 7.5 x 10-4 mm to represent the diameter of a red blood cell because it translates to 7.5 micrometers, which is the actual size of a red blood cell.
Step-by-step explanation:
Madison is deciding which exponent format is best for representing the diameter of a red blood cell in her science report. She can choose between 7.5 x 104 mm and 7.5 x 10-4 mm.
Firstly, understanding what a negative exponent means is crucial. A negative exponent indicates that the decimal point has been moved to the left, as opposed to a positive exponent where it moves to the right. For example, the number 3.47 x 10-3 is equivalent to 0.00347 in standard form, with the decimal point moved three places to the left.
Given that a typical red blood cell is about eight micrometers in diameter, and one micrometer equals 10-6 meters, it's proper to use 7.5 x 10-4 mm. This notation is because 7.5 x 10-4 mm is equal to 7.5 micrometers (since 1 mm = 103 micrometers), which is close to the actual size of a red blood cell. On the other hand, 7.5 x 104 mm equals 75,000 mm, which is drastically larger than a red blood cell and not a practical representation of its size.
Therefore, the correct format for Madison to use in her report is 7.5 x 10-4 mm, and this is how she should write the diameter of a red blood cell in exponent form.