# How to Solve Logic Grid Puzzles: A Worked Example

Source: https://silverapuzzles.com/guides/how-to-solve-logic-grid-puzzles

A logic grid puzzle gives you a few people, a few categories and a list of clues. Mark each clue in the grid with an X (ruled out) or a dot (confirmed). Every time you place a dot, cross out the rest of its row and column, then copy what you know across categories. Repeat until each person has exactly one match in every category.

## How the grid works

Each category gets a block of squares. A square where a row and a column meet answers one question, such as “Does Ana own the dog?”. Mark it with an **×** when the answer is no and a **●** when it is yes. In every row and column of a block there is exactly one ●. So once you place a ●, you can cross out the rest of that row and column. And when only one square in a row is still blank, it must be the ●.

## A worked example

Three friends, Ana, Ben and Cara, each have a different pet (cat, dog, parrot) and a different favorite drink (tea, coffee, juice). The clues:

1. Ben does not own the cat.

2. The parrot owner drinks juice.

3. Ana drinks tea.

4. The cat owner drinks coffee.

**Step 1.** Clue 3 is a direct fact: put a ● at Ana–tea, and cross out Ana–coffee, Ana–juice, Ben–tea and Cara–tea.

**Step 2.** Clue 1 is a direct “no”: × at Ben–cat.

**Step 3.** Clues 2 and 4 link the two categories. The parrot owner drinks juice, but Ana drinks tea, so Ana cannot own the parrot. The cat owner drinks coffee, so Ana cannot own the cat either. Ana’s row now has one blank square left: Ana owns the dog.

**Step 4.** With the dog taken, Ben has only the parrot left (he cannot have the cat), and Cara gets the cat.

**Step 5.** Carry the drinks across: the parrot owner (Ben) drinks juice, and the cat owner (Cara) drinks coffee.

CatDogParrotTeaCoffeeJuice
Ana×●×●××
Ben××●××●
Cara●×××●×
Answer: Ana has the dog and drinks tea, Ben has the parrot and drinks juice, and Cara has the cat and drinks coffee. Every clue checks out, and no other arrangement does.

## Techniques for harder puzzles

- **Transfer what you know.** If Ana is the dog owner, everything true of Ana is true of the dog owner. Copy every × and ● between the blocks; this is where most progress comes from.

- **Read negative clues twice.** “Dexter was not in the Garden, and he did not have the newspaper” is two separate × marks.

- **Use order clues.** “Mr Fenwick sat in a higher-numbered compartment than Ms Gray” means Fenwick is not in compartment 1 and Gray is not in the last one.

- **Use “next to” clues.** If someone sits next to compartment 2, they are in 1 or 3, and nowhere else.

- **Try a branch only as a last resort.** Suppose one option and follow it a few steps. If it breaks a clue, cross it out. Undo everything else you wrote on the way.

## How our mystery cases work

Each [Mystery Mini Case](https://silverapuzzles.com/mystery-case) is a logic grid with a story. Four suspects each have one room (or seat) and one object, and a final rule tells you who the culprit is, such as “Whoever was in the Study took the brooch”. Fill the grid, enter every placement in the verdict table and name the culprit. A program checks that every case has exactly one arrangement that fits all the clues, so you never need to guess.

## Common mistakes

- **Forgetting to cross out.** After every ●, cross out the rest of its row and column in that block.

- **Stopping at one block.** A fact about drinks often finishes the pets block. Check the other blocks after each new mark.

- **Assuming two people can share.** In a standard grid every person has a different answer in each category.

## Frequently asked questions

**What is a logic grid puzzle?**
A deduction puzzle where you match people to items in several categories using clues. A grid of squares lets you mark each possible match as ruled out (×) or confirmed (●).

**What is the best first step in a logic grid puzzle?**
Mark every clue that gives a direct yes or no, then cross out the rest of each row and column that gets a ●.

**Do logic grid puzzles need guessing?**
A well-made one does not. Every mystery case on Silvera PuzzleClub is checked by software to have exactly one solution that follows from the clues.