How can you divide oddly 18 cows in 9 parts?

Answer 1

Here is one possible way:

2 * 1.25

2 * 1.5

5 * 2.5

It is a very odd way of doing it because, in so doing, none of the cows will remain alive.

Suppose you could partition the 18 cows into 9 odd groups.

Now, Odd + Odd = Even

Even + Even = Even

and

Even + Odd = Odd

So, Odd + Odd + Odd + Odd + Odd + Odd + Odd + Odd + Odd = 18

=> Even + Even + Even + Even + Odd = 18

=> Even + Even + Odd = 18

=> Even + Odd = 18

=> Odd = 18 which is false.

Therefore, it is impossible to partition 18 cows into 9 odd groups.