Three different positions of the same dice are shown. Find the number on the face opposite to the one having the number 1.

4

Step 1)     In a dice there are numbers 1, 2, 3, 4, 5, 6

Step 2)  According to question  1  is common in all the dices and it shares it's boundary with all 2, 3 ,5 6 except 4.

Step 3)  So, the number 1 is the face opposite the face showing '4'.