In a dice, 1, 2, 3 and 4 are written on the adjacent faces, in a clockwise order and 5 and 6 at the top and bottom. When three is at the top, what will be at the bottom?

1

Note: In the standard Dice, sum of opposite numbers is always equals to 7.

But as per conditions given in the question:

1,2,3,4 are written on the adjacent faces, in a clockwise order, it means 1 is opposite to 3 and 2 is opposite to 4.

Hence, when 3 is at the top, 1 will be at the bottom.