Step 1: Use the relation between r.m.s. speed and temperature.
For an ideal gas,
\[
v_{\text{rms}}\propto \sqrt{T}
\]
where \(T\) is the absolute temperature in Kelvin.
Step 2: Apply the given condition.
Let the initial temperature be
\[
T_1=0^\circ\text{C}=273\,\text{K}
\]
The r.m.s. speed becomes three times its initial value.
Therefore,
\[
\frac{v_2}{v_1}=3
\]
Using
\[
\frac{v_2}{v_1}=\sqrt{\frac{T_2}{T_1}},
\]
we get
\[
3=\sqrt{\frac{T_2}{273}}
\]
Squaring both sides,
\[
9=\frac{T_2}{273}
\]
\[
T_2=2457\,\text{K}
\]
Step 3: Convert Kelvin into Celsius.
\[
T_2=2457-273
\]
\[
T_2=2184^\circ\text{C}
\]
Step 4: Final conclusion.
Hence, the required temperature is
\[
\boxed{2184^\circ\text{C}}
\]