So firstly lets see how many numbers can be made out of a 3 digit numbers...

and that is = 9*10*10=900

because the first digit cannot be zero so we will reduce the zero from the ten digits.

and the second case for the number to be having three same digits:

if they have three same digits there will be 9 such 3-digit numbers(you know them all).

if they have 2 of the same digits(inclusive of the 3 same digits number and we will remove them)

then there will be 270 such numbers

{111,112,113......

221,222,223,...

............

991......999}

now after removving those 3 same digit numbers we now have (270-9) i.e.261 numbers

now for the different digits we have 900-9-261=630

now the main part

for the thirty generated number's probablilty will all be a numbers with three different digits we have :

630C30/900C30

and for the numbers to be having 2 digits similar we have

261C30/900C30