This classic riddle is built around a sound-alike phrase rather than ordinary arithmetic.
Read “28 chickens” out loud as “twenty ate chickens.” That means 20 of the farmer’s 30 cows ate chickens.
If 20 cows did, then the number that did not is:
30 − 20 = 10.
Answer: 10 cows.
The trick is recognizing that “28” is being used as wordplay. It sounds like “twenty ate,” which completely changes the meaning of the sentence.


