SOLUTION: How many 6 digit Even numbers can be formed by using 1,2,2,4,4,4?

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.