What is the ratio of surface energy of 1 small drop and 1 large drop, if 1000 small drops combined to form 1 large drop

The liquid's volume remains constant, therefore 1000 little droplets have the same volume as one large drop.

$\mathrm{n}\frac{4}{3}{\mathrm{\pi r}}^3=\frac{4}{3}{\mathrm{\pi R}}^3$

$1000{\mathrm{r}}^3={\mathrm{R}}^3\Rightarrow \mathrm{R}=10\mathrm{r}\Rightarrow \frac{\mathrm{r}}{\mathrm{R}}=\frac{1}{10}$

$\frac{(\mathrm{Surface} \mathrm{energy} \mathrm{of} \mathrm{one} \mathrm{small} \mathrm{drop})}{(\mathrm{Surface} \mathrm{energy} \mathrm{of} \mathrm{one} \mathrm{big} \mathrm{drop})}=\frac{4{\mathrm{\pi r}}^2\mathrm{T}}{4{\mathrm{\pi R}}^2\mathrm{T}}=\frac{1}{100}$

Hence the correct answer is 1:100.