TITLE: How to put 9 pigs into 4 pens so that there are an odd number of pigs in each pen?
QUESTION [140 upvotes]: So I'm tutoring at the library and an elementary or pre K student shows me a sheet with one problem on it:
Put 9 pigs into 4 pens so that there are an odd number of pigs in each pen.
I tried to solve it and failed! Does anybody know how to solve this? This question seems ridiculously difficult and impossible IMO.

REPLY [14 votes]: Put 9 pigs into 4 pens so that there are an odd number of pigs in each pen.
  

Each of pens $1,2,3,$ and $4$ have an odd number of pigs in them with $1$ each. The last $5$ pigs are liberally interpreted as being 'put into' the $4$ pens. Though they aren't inside one of the four pens they're inside the four pens.
I didn't see this in the pictured solutions so I thought I'd add it. Apologies if it was already mentioned. It was however mentioned that you could put $1$ in each of the $4$ pens and let the other $5$ roam free. But, what good are your pigs if when you want bacon you discover they walked away? This fixes your bacon in place. Nevertheless, I had fun drawing piggy banks!