Six numbers, 5, 10, 15, 20, 25 and 30, are written on different faces of a dice. Two positions of this dice are shown. Select the number that will be on the face opposite to the face having the number '15'.

30

Step 1) In figure Ist  and IInd  10  is common

Step 2)The number ‘10’ is common in both the dice, but it is at a different position. In order to find out, the number appearing on the opposite face, rotate the dice in a clockwise direction with the common number as the reference.

Step 3)  10     25      30

               10     20      15

Step 4)   25  is opposite to 20

               30   is opposite  to 15

therefore ,

             10  will  be  opposite  to 5 ( AS PER NUMBER GIVEN IN THE QUESTION )