Logic Puzzles: Matching Grids

Methods in this video

Tap a time to jump to where the video teaches that method.

1. 1

   Draw a grid: ticks and crosses

   ▶ 1:24

   When to use it: A few people (days, rooms) are matched one-to-one with a few things: who owns which pet, which sport on which day, which job in which room. Clues say who does not go with what or what must be chosen, and the question asks who gets what, or which one cannot be done.

   • One-to-one matching: draw a grid with people down the side and things along the top; each row gets one tick and each column gets one tick.
   • Turn clues into crosses. Put a tick in a square, then cross out every other square in its row and its column.
   • The clue that settles one person is often about someone else. Put every clue in the grid and none gets missed.
2. 2

   Fill the only choice first

   ▶ 4:35

   When to use it: The grid is big (5 × 5, 4 × 4) with many clues, or a condition is hidden in a sentence ('he wants Friday afternoon free', 'each part must be checked at least twice'), and the question asks where something must go or which ones someone must do.

   • In a big grid, don't start from the thing you are asked about: find a row or column with only one empty square left; that square is the answer for it.
   • Each tick crosses out its row and column, which leads to the next tick.
   • If two are needed and exactly two squares are left, fill both. It's the same idea as only one left.