GATE2013-11

The mass balance for a fluid with density ($\rho$) and velocity ($\overrightarrow{V}$) is
1. $\frac{\partial\rho}{\partial{t}}$ + $\bigtriangledown$.($\rho\overrightarrow{V}$) = 0
2. $\frac{\partial\rho}{\partial{t}}$ + $\overrightarrow{V}$ .($\bigtriangledown\rho$) = 0
3. $\frac{\partial\rho}{\partial{t}}$ + $\rho$($\bigtriangledown\overrightarrow{V}$) = 0
4. $\frac{\partial\rho}{\partial{t}}$ –  $\overrightarrow{V}$.($\bigtriangledown\rho$) = 0