Six identical cells, each of emf of $6V$, are connected in parallel. The net emf across the battery is

$\begin{array}{l} \Rightarrow \frac{1}{\mathrm{r}_{\text {eff }}}=\frac{1}{\mathrm{r}}+\frac{1}{\mathrm{r}}+\frac{1}{\mathrm{r}}+\frac{1}{\mathrm{r}}+\frac{1}{\mathrm{r}}+\frac{1}{\mathrm{r}} \\ \mathrm{r}_{\mathrm{eff}}=\frac{\mathrm{r}}{6} \end{array}$

all cells are connected in parallel so the total current flowing from the combination of all cells will be divided equally in all cells. hence total current in circuit is equal to sum of individual current passing out from each cell.

$\frac{E_{\text {eff }}}{r_{\text {eff }}}=\frac{E}{r}+\frac{E}{r}+\frac{E}{r}+\frac{E}{r}+\frac{E}{r}+\frac{E}{r}$

$E_{\text {eff }}=E=6 V$