MEPX
Chapter 2 of 11All chapters
  1. 1How puzzles trick you
  2. 2All, some and none
  3. 3If, then
  4. 4Common fallacies
  5. 5Number sequences
  6. 6Words into equations
  7. 7Rate and work problems
  8. 8Elimination grids
  9. 9Knights, knaves and self reference
  10. 10Reading exactly
  11. 11Building the habit

Chapter 2 of 11

All, some and none

What a statement about a group licenses.

Some is not all

A statement about some members tells you nothing about any particular member. All roses are flowers and some flowers fade quickly, but the fast fading ones might all be tulips.

  • "Nothing here settles it" is a real answer and often the correct one.
  • The negation of "all are" is "at least one is not", not "none are".

Drawing it

Two overlapping circles settle most of these questions in seconds. Put roses inside flowers, shade the fast fading part of flowers, and see that the shading need not touch roses.