Some puzzles require a mind for math, others a keen eye. Then there are brainteasers that are so nonsensical the biggest challenge is saying them with a straight face. The "cows and chickens" riddle falls into the latter group.

You can hear the riddle in the video below shared by digg. The filmmaker’s parents can’t listen to the question without cracking up, and after thinking about it for a few seconds you may start to feel a bit hysterical as well. But keep watching: If you listen to the phrasing close enough, you may be able to sort out the sentences before the clip ends.

The riddle can only be listened to, not read, so stop here if you still want to get to the bottom of it on your own.

The reason it’s so tricky is that it sounds like an incomplete thought when read aloud. The parents hear, “There are 50 cows and 28 chickens. How many didn’t?” which is nonsense.

But the answer suddenly presents itself when the question is written out correctly. What the son is really asking is: “There are 50 cows, and 20 ate chickens. How many didn’t?” Once you’ve caught the sneaky word play, you can use simple subtraction to conclude that the answer is 30. Save that one for your next family get-together.

[h/t digg]