Two positions of a block are shown below (i) and (ii). When 2 is at the bottom which number will be at the top?

Number three is common in both the figures we assume the block in figure (ii) to be rotated so that three appears at the same position as in figure (i) and the numbers 5 and 2 move to the faces hidden behind the numbers 4 and 6 respectively. Thus the combined figure will have 3 on right hand side face, 4 on the front face, 6 on the top face, 5 on the rear face and 2 on the bottom face. Clearly when 2 is at the bottom, then 6 is at the top.