How many positive odd integers less than 10,000 can be represented using the digits 0, 3, 6 an 9?

Answer 1

Last digit:0 or 9 (2 choices)
second to fourth digits, 4 choices each.
Total number of four digit odd integers
=4*4*4*2
=128
(these include 9999 and 0009, etc.)

Answer 2

125