How many 3 digit even numbers can be formed from the digits 1, 2, 3, 4, 5, 6 if the digits can be repeated ?

Even numbers are those numbers which has in its unit place the digits 2, 4 and 6.
Therefore the unit digit can be filled up in 3 ways.
However since repetition is allowed, the tens and hundreds place can be filled 6 ways each. Hence, the required number of numbers: 6 × 6 × 3 = 108.