Step 1: Use the formula for the root mean square velocity.
The \( v_{\text{rms}} \) is related to the temperature by \( v_{\text{rms}} = \sqrt{\frac{3kT}{m}} \). The temperature is in Kelvin, so we first convert the temperatures:
- Initial temperature = \( 27°C = 300 \, \text{K} \)
- Final temperature = \( 127°C = 400 \, \text{K} \)
Step 2: Calculate the percentage increase.
The percentage increase in \( v_{\text{rms}} \) is given by:
\[
\frac{v_{\text{rms, final}} - v_{\text{rms, initial}}}{v_{\text{rms, initial}}} \times 100 = 15.5\%
\]
Final Answer:
\[
\boxed{15.5\%}
\]