Answer:
Total number = 3000
Explanation:
Odd digit numbers = 1,3,5,7,9
Total no. of odd digit numbers = 5
Numbers which aren't odd = 0,2,4,6,8
Total no. which aren't odd = 5
For a 4 digit number.
If all Fours digits are odd:
Total numbers = 5×5×5×5 = 625
If first digit is not odd and last three digits are odd:
Total numbers = 4×5×5×5 = 500
(0 cannot be put at first digits place)
If second digit is not odd and rest three digits are odd:
Total numbers = 5×5×5×5 = 625
If third digit is not odd and rest three digits are odd:
Total numbers = 5×5×5×5 = 625
If fourth digit is not odd and rest three digits are odd:
Total numbers = 5×5×5×5 = 625
Add all of them we get:
Total number = 625+500+625+625+625 = 3000