The unit's place of the 2-digit number can be filled in 2 ways (2 or 4). The ten's place of the 2-digit number can be filled in 5 ways (1,2, 3, 4 or 5) since repetition is allowed. So the number of two-digit even numbers that can be formed *with repetition* is 2 x 5 = 10. The 10 permutations are: 12, 22, 32, 42, 52, 14, 24, 34, 44, 54.

Now if repetition were not allowed, the ten's place can be filled only 4 ways since one of the even numbers is used in the unit's place. So the number of two-digit even numbers that can be formed *without repetition* is 2 x 4 = 8. The 8 permutations are: 12, 32, 42, 52, 14, 24, 34, 54. Note: we can't form 22 and 44 in this case.