3750.31 – Yobs, Blobs, and Slobs

Suppose we know that (1) Some Yob is not a Slob, and (2) No Slob is a Blob.

If “some” means “at least one”, then we can conclude which of these?

  1. Some Yobs are not Blobs.
  2. Some Blobs are not Yobs.
  3. No Yob is a Blob.
  4. Some Yobs are Blobs.
  5. None of the above.
Solution

A Venn diagram of this situation is below. We cannot tell whether the three regions marked with a question mark are empty or not. The problem is that while there mustmust be a Yob who is not a Slob (this is assumption 1), this particular Yob might or might not be a Blob. Therefore, we can’t deduce I or II or III or IV. The correct answer is V.

3750_31_solution_727af100f8.png