How many four digit even numbers can be formed from digits 1,2,3,4,5 if repetition is allowed.

how can solve this using permutation formula

Step-by-step explanation:

5*5*5*2

The number must end in 2 or 4.

1 3 and 5 will give you an odd number if either is at the end.

The permutation formula does not lend itself to this problem. That is because repetition is allowed. So 5554 is a possible answer.

You can choose any one of 1 to 5 for the first place.

1 to 5 in the second place independent of what you choose for the first place.

The only thing restricting you is the last place. It must be 1 of 2.

I suppose you could use 2P1 for that.

5 * 5 * 5 * 2P1