maaverick wrote:

I'll go with (D)

Not the most elegant way, but an approach, nevertheless, on the basis of POE.

Let the weight of the partially filled box be 100 => weight of water = 90 and weight of box = 10. If the completely filled box weighs double the partially filled box, it follows that just less than half the box is filled with water (because the weight of the completely filled box would include the weight of the box as well). This rules out (a), (b), (c) and (e) and leaves us with (d).

It would be great if you could post the OA with explaination.

Thanx all. good explanaions, maaverick, gyatri and banerjee.