Roboku
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Case 19: who took the Giant Pearl?
During the night rounds at the aquarium, a guard raised the alarm: the Giant Pearl, which should be in the Main Aquarium, is missing. Everything points to the thief still being among those present. Help the police unmask them.
The board
- 1Café
- 2Terrace
- 3Laboratory
- 4Gift Shop
- 5Restrooms
- 6Tank Room
- 7Maintenance Room
- 8Storage Room
- 9Main Aquarium
- Seat: anyone can be on it.
- Shelf: no character can stand on its cell, but the stolen item can be there.
- Table: nothing can be on its cell.
- Window: the blue line on a wall.
Suspects and clues
- JJavier
He's next to a wall. - HHugo
He's in column D. - NNoah
He's in the Laboratory. - TTariq
He's not next to any wall. - MMartha
She's 5 rows away from the Maintenance Room. - YYusuf
He's in row 6. - GGiant Pearl (stolen item)
It's 5 columns away from the Laboratory.
Remember the rules: no two suspects (nor the item) ever share a row or a column, each character is in a different room, and the thief is the only one sharing a room with the stolen item. Unsure? Read how to play and the clue types.
Solution
Try it yourself first: pen and paper are enough. When you want to check, open the reasoned solution.
Show the step-by-step solution
- Javier's clue: He's next to a wall. 38 cells remain possible.
- Hugo's clue: He's in column D. 5 cells remain possible: D3, D4, D5, D6 and D7.
- Noah's clue: He's in the Laboratory. 2 cells remain possible: F1 and F2.
- Tariq's clue: He's not next to any wall. 6 cells remain possible: B2, C3, B5, E5, B6 and E6.
- Martha's clue: She's 5 rows away from the Maintenance Room. It leaves a single cell: G7.
- Yusuf's clue: He's in row 6. 6 cells remain possible: B6, C6, D6, E6, F6 and G6.
- The stolen item's clue: It's 5 columns away from the Laboratory. It leaves a single cell: A2.
- Martha can only be on G7. No one else can be in row 7 or column G, and no other character can be in the Main Aquarium.
- The Giant Pearl can only be on A2. No one else can be in row 2 or column A.
- F2 has already been ruled out, so Noah can only be on F1. No one else can be in row 1 or column F, and no other character can be in the Laboratory.
- Every cell still open to Hugo is in column D, so no one else can be in that column.
- Every cell still open to Yusuf is in row 6, so no one else can be in that row.
- Proof by contradiction. Suppose Hugo were on D3. Following the rules above, there wouldn't be enough rooms left for every character. So Hugo is not on D3.
- Proof by contradiction. Suppose Javier were on B4. Following the rules above, Yusuf would be left with no possible cell. So Javier is not on B4.
- Proof by contradiction. Suppose Javier were on C4. Following the rules above, there wouldn't be enough rows left for everyone. So Javier is not on C4.
- Proof by contradiction. Suppose Hugo were on D5. Following the rules above, there wouldn't be enough rows left for everyone. So Hugo is not on D5.
- D3, D5, D6 and D7 have already been ruled out, so Hugo can only be on D4. No one else can be in row 4 or column D, and no other character can be in the Terrace.
- Proof by contradiction. Suppose Javier were on E3. Following the rules above, there wouldn't be enough rooms left for every character. So Javier is not on E3.
- Proof by contradiction. Suppose Javier were on C5. Following the rules above, Tariq would be left with no possible cell. So Javier is not on C5.
- Every other cell the clue allowed has already been ruled out, so Javier can only be on B3. No one else can be in row 3 or column B, and no other character can be in the Storage Room.
- B2, C3, B5, B6 and E6 have already been ruled out, so Tariq can only be on E5. No one else can be in row 5 or column E, and no other character can be in the Gift Shop.
- B6, D6, E6, F6 and G6 have already been ruled out, so Yusuf can only be on C6.
Conclusion: Javier is the only person sharing the Storage Room with the Giant Pearl, which is on A2. He is the thief.