A cylindrical tank of diameter 35 cm is full of water. If 11 litres of water is drawn off, the water level in the tank will drop by :

Let the drop in the water level be h cm
Then,
$$\eqalign{ & \Rightarrow \frac{{22}}{7} \times \frac{{35}}{2} \times \frac{{35}}{2} \times h = 11000 \cr & \Rightarrow h = \left( {\frac{{11000 \times 7 \times 4}}{{22 \times 35 \times 35}}} \right){\text{ cm}} \cr & \Rightarrow h = \frac{{80}}{7}{\text{ cm}} \cr & \Rightarrow h = 11\frac{3}{7}{\text{ cm}} \cr} $$