To find the thickness of a fingernail, we start with the diameter of a human hair, which is given as \(4 \times 10^{-5}\) inches. According to the problem, a fingernail is about \(0.011\) inches thicker than this.
Now, we can calculate the thickness of the fingernail:
\[ \text{Thickness of a fingernail} = \text{Thickness of a human hair} + 0.011 \text{ inches} \]
\[ \text{Thickness of a fingernail} = 4 \times 10^{-5} + 0.011 \]
To add these two values, we first convert \(0.011\) into a decimal form that can be added directly:
\[ 0.011 = 0.011000 \]
Now, we align the numbers for addition:
\[ \begin{array}{r} 0.011000 \
- 0.000040 \ \hline 0.011040 \ \end{array} \]
Thus, the thickness of a fingernail is \(0.011040\) inches.
Rounding this to three decimal places gives:
\[ 0.011 \]
Therefore, the thickness of a fingernail is approximately \(0.011\) inches.