To find the thickness of a fingernail, we start with the diameter of a human hair, which is approximately \( 4 \times 10^{-3} \) inches.
Next, we need to account for the additional thickness of the fingernail, which is given as \( 0.011 \) inches thicker than the hair.
To calculate the thickness of the fingernail, we add the thickness of the hair to the additional thickness:
\[ \text{Fingernail thickness} = \text{Hair thickness} + \text{Additional thickness} \]
Substituting in the values:
\[ \text{Fingernail thickness} = 4 \times 10^{-3} + 0.011 \]
First, we convert \( 0.011 \) inches to a decimal representation:
\[ 0.011 = 0.011 \]
Now, we convert \( 4 \times 10^{-3} \) into decimal form, which is:
\[ 4 \times 10^{-3} = 0.004 \]
Now we add the two decimal values together:
\[ 0.004 + 0.011 = 0.015 \]
Thus, the thickness of the fingernail is \( \boxed{0.015} \) inches.