Every healthy duck is greedy and every old duck is greedy.
On a particular farm, some ducks are greedy and some ducks are not.

Which of the following statements about the ducks on that farm must be true?

1. There are both young ducks and old ducks.
2. All the ducks that are not greedy are young.
3. Some of the young ducks are sick.
4. All the sick ducks are young.

This problem is taken from "Sums for Smart Kids" by Laurie Buxton, published by BEAM Education.
To obtain a copy call the BEAM orderline on $020 7684 3330$. (Price: $£17.50$ plus handling and delivery.)