How Many Cows Are Left?

Here is another STEP homework question, which is a famous riddle.

Puzzle. Peter had ten cows. All but nine died. How many cows are left?

The wording is confusing on purpose. So, the students who are in a hurry subtract nine from ten and answer that only one cow is left. This answer is wrong. All but nine means that one cow died. So, the correct answer is nine.

One of my students decided that nine is the name of one of the cows, though it should have been capitalized. This means that all the cows except for Nine died, and only one cow, Nine, is left.

This student managed to find a legitimate explanation for the standard wrong answer.



  1. George R.:

    And what if Peter is the mother-cow? Ten is left in this case…😊
    (And what if Ten is also a name?…🤔)

  2. Leo B.:

    The wording is confusing, indeed. It is not clear that “how many are left” refers to live cows. Perhaps it’s the one which died is left lying dead, and the remaining nine went to greener pastures.

  3. Robert L.:

    ChatGPT 3.5: The statement says that all but nine cows died, so only one cow is left.

  4. Rosalie:

    “The wording is confusing on purpose.” And for this reason the question should be rejected. If a question is to be teaching-material (i.e. where the teacher knows the answer and the purpose of asking is to see if the pupils can work it out) then it should be absolutely clear and unambiguous.

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