A plot of land in the form of a rectangle has dimensions 240 m × 180 m. A drain-let 10 m wide is dug all around it (outside) and the earth dug out is evenly spread over the plot, increasing its surface level by 25 cm. The depth of the drain-let is :

Answer: Option C

Volume of earth dug out :
= (240 × 180 × 0.25) m³
= 10800 m³
Let the depth of the drain-let be h metres
Then, Volume of earth dug out :
= [{(260 × 200) - (240 × 180)}h ] m³
= (8800h) m³
∴ 8800h = 10800
⇒ h = $$\frac{10800}{8800}$$
⇒ h = $$\frac{27}{22}$$
⇒ h = 1.227 m