The capacity of a cylindrical tank is 246.4 litres. If the height is 4 metres, what is the diameter of the base ?

Answer: Option D

Volume of the tank = 246.4 litres = 246400 cm³
Let the radius of the base be r cm
Then,
$$\begin{array}{rl}& \left(\frac{22}{7}\times r^2\times 400\right)=246400\\ & \Rightarrow r^2=\left(\frac{246400\times 7}{22\times 400}\right)\\ & \Rightarrow r^2=196\\ & \Rightarrow r=14\end{array}$$
∴ Diameter of the base = 2r = 28 cm