11111
There are 5 numbers which can make the 3 digit numbers in this example. Therefore each digit in the 3 digit number has 5 choices of which number can be placed there. Therefore number of 3 digit numbers = 5 x 5 x 5 = 125
12346
Not sure what a "didget" is. It is possible to make 18 5-digit numbers.
The first digit can be any one of 1,2,3,4,5. With each choice of digit1, the second digit can be any one of 1,2,3,4,5 so making 5*5 two-digit numbers. With each of these, the third digit can be any one of 1,2,3,4,5 so making 5*5*5 three-digit numbers and so on. The total number is 55 = 3125.
The smallest 5 digit number is 10000 = 1002 The largest 5 digit number is 99999 and 3162 < 99999 < 3172 So, take any number between 100 and 316 (both inclusive) and square it to get a 5-digit perfect square.
The question is a bit ambiguous: "the sum of the product ... " does not seem to make sense. The first 5 digit number is 10000 the first 5 digit multiple of 6 is 10002 Their product is 100020000. I am not sure what to sum, though.
00000 or 00001
99996
13,579 or .13579 . If I'm allowed to repeat digits, then you are 11,111 or .11111 .
The largest 5 all odd digit number is 99999, which makes the rest of the question meaningless. 59713 if you think the information is not meaningless
The tenths digit is 5