The probability for rolling an even number on a number cube would be 3/6 or 50%. There are 6 sides to a cube and 1,3,5 (3 sides) are odd, 2,4,6 (3 sides) are even.
The probability of flipping a tails on a coin is 1/2 or 50%. There are two sides on a coin and 1 side is tails.