Four different positions of the same dice are shown below. Find the number on the face opposite the face showing 4.

We can solve this easily by comparing Position (i) and Position (iv):
* In Position (i), the visible faces are 2, 3, and 4.
* In Position (iv), the visible faces are 2, 3, and 1.

Notice that faces 2 and 3 are common to both positions. According to the rules of dice, when two positions of the same dice have two common faces, the remaining uncommon faces on both positions are opposite to each other.

Therefore, the face showing 4 is opposite to the face showing 1.