A rectangular piece of land measures 240 meters by 180 meters. A 10-meter-wide drain is excavated all around the outside of the land. The soil removed from the drain is evenly spread over the land, raising its surface level by 25 centimeters. What is the depth of the drain?

Explanation

The drain is dug around the plot, increasing the total area. The volume of earth removed equals the volume spread over the plot, raising its level by 0.25 meters. Using volume balance and dimensions, the depth of the drain calculates to approximately 1.227 meters.