To find the length of the femur for a male who is 71 inches tall using the formula provided, we can rearrange the formula \( \text{height} = 1.88f + 32.01 \) to solve for \( f \).
Starting with the original equation:
\[ \text{height} = 1.88f + 32.01 \]
Substituting the height (71 inches) into the equation:
\[ 71 = 1.88f + 32.01 \]
Next, we will isolate \( f \) by first subtracting 32.01 from both sides:
\[ 71 - 32.01 = 1.88f \]
\[ 38.99 = 1.88f \]
Now, divide both sides by 1.88 to solve for \( f \):
\[ f = \frac{38.99}{1.88} \]
Calculating this gives:
\[ f \approx 20.74 \]
To the nearest inch, the length of the femur is approximately \( 21 \) inches.
Therefore, the correct answer is:
21 inches