The approximate percentage reduction in the volume of a cube of ice if each side of ice cube is reduced by 0.7 percentage due to melting is

$$\begin{gathered} \frac{\mathrm{\delta x}}{\mathrm{x}}\times 100=-0.7 \\ V=x^3\Rightarrow \log V=3 \log x\Rightarrow \frac{\mathrm{\delta V}}{\mathrm{V}}=3\cdot \frac{\mathrm{\delta x}}{\mathrm{x}} \\ \Rightarrow \frac{\mathrm{\delta V}}{\mathrm{V}}\times 100=3\cdot \frac{\mathrm{\delta x}}{\mathrm{x}}\times 100=3(-0\cdot 7)=-2\cdot 1 \end{gathered}$$

i.e. the approximate percentage reduction in the volume of cube of ice $=2.1$