elementary math cardinal numbers

Question

what is the cardinal number of {5,7,9...113}

Answer 1

{5, 7, 9, ...,113}

the natural numbers from 1 to 114 gives us 114 numbers

57 are even and 57 are odd

the given set has all of the odd numbers except 1 and 3

therefore there are only 57-2=55 odd numbers

Answer 2

A cardinal number tells us how many are there. In this case, the set has {5, 7, 9, ..., 113}.

5 → 1 ; 7 → 2 ; 9 → 3 ; 11 → 4 ; ... 23 → 10 ; ... 43 → 20 ; ... 63 → 30 ; ... 83 → 40 ; ... 103 → 50 ; ... 113 → 55

Normally, there would be 113 numbers in the set.

First, I take away 4 from 113 to get 109 because the first 4 numbers are not in the set.

Second, I take half away from 109 to get around 55 because all even numbers are not in the set.

Therefore, the cardinal number in the set is 55.