Four positions of a dice are shown below. What number must be at the bottom face when the dice is in the position as shown in the figure(iii)

From figures (i), (ii), (iv) we conclude that 5, 6, 1 and 2 lie adjacent to 4. Hence, 3 must lie opposite 4 and vice-versa. In fig. (iii), 3 is at the top and consequently 4 must lie at the bottom face.