Dimention of the tank = 20x15x15
Lenght = 20 cm
Width = 15 cm
Height = 15 cm
Assume the height of the water = h cm
Volume of the water = 20x15xh cm3
1 cm3 = 1/1000 litre
Water = 20x15xh/1000 litres = 2.4 litres
=> h = 2400/(20x15)
Hence the height of the water (h) = 8 cm