9 odd numbers less than 100 can be formed. They are:
3,5,7,35,37,53,57,73 and 75.
There are 2000 such numbers.
if the repetition is allowed the there is 6*6*6 possible ways = 216
# 230 # 203 # 320 # 302
If repetition is allowed and leading zeros are allowed, then you have 000 to 999, which is 1,000 possibilities (I will not list them here). If no leading zeros are allowed, then you have 100 through 999, so there are 900 possibilities. If there are other restrictions, such as no repetition, then I'll refer you to the related link at MathsIsFun.com
There are 25 such numbers.
64 if repetition is allowed.24 if repetition is not allowed.
If repetition of digits isn't allowed, then no13-digit sequencescan be formed from only 5 digits.
125
There are 2000 such numbers.
It is 415968.
There are 2000 such numbers.
Possible solutions - using your rules are:- 11,13,17,31,33,37,71,73 &77
125 There are five choices for each of the three digits (since repetition is allowed). So there are 5*5*5=125 combinations.
20 of them, if repetition is not allowed.
If repetition is allowed . . . . . 343 If repetition is not allowed . . . . . 210
Just six numbers... 345, 354, 435, 453, 534 & 543
15 of them.