A rectangular tank is 225 m by 162 m at the base. With what speed must water flow into it through an aperture 60 cm by 45 cm that the level may be raised 20 cm in 5 hours?

Given, Length of the rectangular tank = 225 m

Breadth of the rectangular tank = 162 m 

height of rectangular tank = 0.2 m

Volume of the water to be filled in tank = 225 x 162 x 0.2 = 7290 m$$^{3}$$

Speed of the flowing water in the aperture per hour is given by,

= $$\frac{7290}{5 \times (60/100) \times (45/100)}$$

= $$\frac{7290 \times 100 \times 100}{5 \times 60 \times 45}$$

= $$\frac{72900000}{13500}$$

= $$5400$$m/hr

Hence, option B is the correct answer.