The percent of error in his measurement is:
25%
The percent error is calculated by the formula:
[tex]\text{Percent error}=\dfrac{|\text{Recorded measurement-Actual measurement}|}{\text{Actual measure}}\times 100[/tex]
Roger has a nail that is 12 centimeters long he measures and records the length of the nail at 15 centimeters.
Hence,
[tex]\text{Percent error}=\dfrac{|15-12|}{12}\times 100\\\\\text{Percent error}=\dfrac{3}{12}\times 100\\\\\text{Percent error}=25\%[/tex]
Hence, the percent error is: 25%.