Find the surface area of the water in the aquarium if 15 liters of water fill it by 2.5 decimeters (1l = 1dm).

1. Let’s convert the volume of water in the aquarium into a value suitable for calculations:
15 liters (l) = 15 cubic decimeters (dm3);
2. The water in the aquarium is a parallelepiped with a height of 2.5 decimeters and a volume of 15 cubic decimeters;
3. Knowing this, we determine the surface area of the parallelepiped:
15 / 2.5 = 6 (dm2);
4. The surface area of the parallelepiped is the surface area of the water in the aquarium;
Answer: The surface area of the water in the aquarium is 6 square decimeters.