Solution :
$C_s= \large\frac{1}{3} +\frac{1}{3} +\frac{1}{3}$
$C_p=3+3+3=9$
$\quad= 9 \mu F$
Energy when connected in series is $\large\frac{1}{2} $$C_sv^2$
$E_s= \large\frac{1}{2}$$\times 1 \times v$
Energy when connected in parallel is $\large\frac{1}{2} $$C_pv^2$
$E_p= \large\frac{1}{2} $$ \times 9 \times v$
$\therefore \large\frac{E_s}{E_p}= \frac{1/2 \times 1 \times v}{1/2 \times 9 \times v}$
$\qquad= 1:9$