Two positions of a dice are shown below. When number 1 is on the top, what number will be at the bottom?

Number 6 is common to both the positions of the dice. We assume the dice in fig. (ii) to be rotated so that 6 remains on the top face (i.e. face V as per activity 1) and the number 4 in fig. (ii) moves to the FR-RH face (i.e. face I) as in fig. (i), then 5 will move to the RR-RH face (i.e. face II). Clearly, 5 (which lies on face II) and 1 (which lies on face IV) will be opposite to each other. So, when 1 is on the top, then 5 will be at the bottom.