In such numbers, the digit "1" can occupy any position, except the "ones" position.


There are    different even numbers, comprising of given digits and having "1" in the most-left position.


      (   is the number of distinguishable arrangements of the digits 2,2,4,4,4 )


There are    different even numbers, comprising of given digits and having "1" in the 2-nd position from the left.


    . . . .  and so on . . . 


There are    different even numbers, comprising of given digits and having "2" in the 5-nd position from the left.


In this way, you get all possible distinguishable arrangements, and their total number is   =  = 5*10 = 50 numbers.