Explanation:

Each even number must have  2, 4, or 6 in its units, place.
total number of digits = 5
Units place can be filled up by anyone of the three
digits 2, 4, and 6 in 3 ways.
Hundreds place can be filled up by any one of the
remaining four digits in 4 ways.
Remaining one place can be filled up by the remaining
three digits in 3P1 ways.
numbers formed = 4 × 3 × 3P1 = 12 × 3! /2!
                                                             
= 36