So we have a cube with sides numbered form 1 to six and we want to know what is the experimental probability of rolling either a 3 or a 6. So the probability of rolling any number from 1 to six is 1/6 because a cube can fall only on one side. But we need either 3 or a 6 so the probability of the cube falling on a side we want is double of 1/6 and that is 2/6=1/3.
