Now we know volume of water flowing out per second from the hole of area a is given by
Volume / second $= a v$
Where v= velocity of e flux
$v= \sqrt {2gh}$
$\therefore $ Time taken to empty water equal to volume of water initially present $t =\large\frac{A \times h}{av}$
$A$ = Area of vessel
$h$ = height of water
$t=\large\frac{A}{a} \sqrt{\frac {h}{2g}}$
$\quad= 100 \sqrt {\large\frac{2}{2 \times 9.8}}$
$\quad=\large\frac{100}{\sqrt {9.8}}$
$\quad \approx 32\;seconds$