Question

$\frac{U_{rms},2}{U_{rms},1} = \frac{1}{2} = \sqrt{\frac{T_{2}}{T_{1}}} \Rightarrow \frac{1}{4}$

Now $T.V^{\gamma - 1}$= constant

$\Rightarrow \frac{T_{2}}{T_{1}} = \left( \frac{V_{1}}{V_{2}} \right)^{\gamma - 1} \Rightarrow \frac{1}{4} = \left( \frac{V_{1}}{V_{2}} \right)^{7/5 - 1} $$$\therefore V_{2} = 32\text{ }\text{V}_{1}$$