Two different positions of the same dice are shown, the six faces of which are numbered from l to 6. Select the number that will be on the face opposite to the one showing '6' .

1

Step 1) In figure 5  and 4

Step 2) Compare both the figure and we find out 5 and 4 both are common

Step 3)  Therefore 1 is the number which will be opposite to 6