When You're Stuck on a Logic Grid Puzzle

Going further, part 5 of 5 of How to Solve Logic Grid Puzzles.

These puzzles are built to be solved by logic alone. Being stuck means there is a step you haven't spotted yet, not that you have to guess.

A checklist

Work down this list, and start again from the top whenever you place a new mark.

1. Last empty squares. Scan every row and column of each small grid for one with a single empty square. See finishing the grid.
2. Carry across. For each circle, compare the two items' rows and columns in the other grids, and copy X's and circles from one to the other.
3. Reread each clue.
   • Either/or: has one option been ruled out? Then the other is true.
   • Greater than: has either item lost an option? Then so has the other, one gap away.
   • Pair: do you know either half? Then you know the other.
   • All different: has every pair in the list got its X?
4. The harder techniques.
   • A second look at either/or and pair clues
   • Combining two greater-than clues
   • No options in common
   • Locked squares

Take notes

Greater-than clues are easier to combine when they are written down in order. A line such as "Samuel, then Lillie 1 year later" or "Monsters + 3 = Yang" takes a few seconds to write. Putting two of them side by side often shows a link you hadn't seen.

Use a hint

In the app, a hint marks the next square and tells you the reasoning behind it. Read the reasoning before moving on, so the same step is easier to find next time.

If a hint makes no sense, the grid may hold a mistake. The app can erase any wrong marks for you.

Trial and error, as a last resort

You never need to guess, but a careful guess can get you moving again.

1. Pick an item with only two squares left.
2. Mark one of them as a circle, and remember that it was a guess.
3. Follow it through with the ordinary moves.
4. If you reach something impossible, such as a row with no squares left, the guess was wrong. Undo back to it and mark the other square. That one is certain.
5. If nothing goes wrong, you have learned nothing certain. Undo back to the guess and try a different item.

The app's undo goes back as far as you need, which makes this safe to try.

Previous: Locked squares
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