Four positions of a dice are given in the question figures. Identify the number at the bottom when top's is 6.

On the basis of question figure pattern ,
From the given views of dice it is clear that the numbers 2, 3, 4, and 5 cannot be on the face opposite 1.
Hence, 6 must be on face opposite 1.
Therefore, when 6 is on the top face 1 must be on the bottom face.