Answer: 0.6 meters cubed.
Explanation:
To find the answer to this, first find the volume of the cube.
Volume is equal to the side cubed. In this case, 1 cubed is 1, so the area of the cube is 1 meter cubed.
The depth of the water is 0.4 meters, so the water makes a shape of a rectangular prism, where the length and width are 1 meter, and the height is 0.4 meters.
The volume of a rectangular prism is l*w*h, so the volume of this rectangular prism is 0.4 * 1 * 1, or 0.4 meters cubed.
As such, the volume of the air in the tank is 1 - 0.4, or 0.6 meters cubed.