How many 3 digit numbers are odd show working please?

Answer 1

The first (hundreds) digit can be chosen in any one of 9 ways from the digits {1,2,3,...,9}.

With each one of these, the second (tens) digit can be chosen in any one of 10 ways from the digits {0,1,2,3,...,9}.

With each of these combinationsm the third (units) digit can be chosen in one of 5 ways from the digits {1,3,5,7,9}.

Altogether, then, there are 9*10*5 = 450 ways or 450 odd 3-digit numbers.