This permutation problem depends on whether the numbers are allowed to be repeated. If they are, there are a possible 9999 numbers, starting with 0001 and running sequentially to 9999. If they are not allowed to be repeated, there are a possible 5040 combinations.
9 odd numbers less than 100 can be formed. They are: 3,5,7,35,37,53,57,73 and 75.
If the digits can be used more than once, then 900. If not, then 648.
There are 25 such numbers.
# 230 # 203 # 320 # 302
There are 7*94 = 45927 such numbers.
10,000
100000 - including numbers with leading 0s
There are 2000 such numbers.
There are 76 such numbers. Eight more if you allow numbers to start with 0.
9 odd numbers less than 100 can be formed. They are: 3,5,7,35,37,53,57,73 and 75.
151200 numbers.
192, including ones containing repeat digits.
103 and 301 .
"130" and "310" .
If the digits can be used more than once, then 900. If not, then 648.
2,401
There are 25 such numbers.