Question

How many even two digit numbers have an odd numbers as the sum of their digits?

Answer 1

The sum of two digit is odd if and only if one of the digits is odd and other is even.

So,

If the first digit is odd and second digit is even,

then the candidates for the first digits can be {1,3,5,7,9} and the candidates for 2nd digit is {0,2,4,6,8}

So there are a total of 25 numbers having their sum as odd numbers