The storage tank is a cube of volume 4096 m3
Let Side of cube = a m
Volume of cube,
a3=4096a=3√4096 =3√16×16×16∴a=16 m
The present depth of water = 12 m.
∴ Depth of water already used, h′=16−12=4 m
∴ Volume of water used
=a×a×h′=16×16×4=1024 m3