Question

a human hair is 75.0 μm across. how many inches is this?

Explanation:

Step1: Recall conversion factors

We know that 1 inch = 2.54 cm and 1 cm = 10000 $\mu$m. So 1 inch = 2.54×10000 $\mu$m = 25400 $\mu$m.

Step2: Set up the conversion

To convert 75.0 $\mu$m to inches, we use the conversion factor $\frac{1}{25400}$ inches per $\mu$m. So the calculation is $75.0\times\frac{1}{25400}$.

Answer:

$75.0\times\frac{1}{25400}\approx0.00295$ inches