Answer:
For the hundereds digit, there are 3 possibilities i.e 4,5 or 6——(1)
For the ten digit, there are 2 possibilities [As one of the numbers has been used for the ones digit]——(2)
For the hundereds digit, there is 1 possibility [As 2 digits have been used for Hundereds and tens]——(3)
Therefore, The number of digits without repetition is 3*2*1=6
With repetition is 3*3*3=27
