**Disclaimer**

The puzzle I used in this post appears in the book titled, “Brain Games: Lower Your Brain Age in Minutes a Day.” The contributing writer for the book is Holli Fort and the puzzle editor is Fraser Simpson. Brain Games is a trademark of Publications International, Ltd. Louis Weber, CEO of Publications International, allowed me to use the puzzle in my post. I chose to write this post because solving, and attempting to solve, an ABCD puzzle is a fantastic brain exercise.

**Instructions**

According to the book, “Every cell in the grid contains one of four letters: A, B, C, or D in each square of the grid. No letter can be horizontally or vertically adjacent to itself. The tables above and to the left of the grid indicate how many times the letter appears in that column or row.” The goal is to fill each cell with the correct letter, such that all cells contain a letter that does not violate the puzzle rules. Can you complete the grid?

**Puzzle**

**General Tips for any 6 x 6 ABCD Puzzle**

Tip 1: Use a pencil, rather than a pen, and keep an eraser nearby.

Tip 2: One of the easiest cells to solve is usually in row or column that contains three of the same letter, when the row or column touches (vertically or horizontally) a cell in which the content is known. Any row or column that contains three of the same letter MUST include that letter in one of the first two cells, in one of the middle two cells, and in one of the last two cells of that row or column.

**Specific Hints for this Puzzle**

Do not read anything in this section unless you are absolutely certain you need a hint to solve the puzzle. The following hints are not the only hints applicable to the ABCD puzzle in this post. Similarly, the strategy I used to solve the puzzle in this post is not the only strategy. I added the red letters and numbers below and to the right of the grid to improve communication and understanding. The “D” in the far right column is located at the intersection of column R and row 5 (R5). Similarly, the “D” in the bottom row is located at the intersection of column Q and row 1 (Q1).

Hint 1: The puzzle tells us row 1 includes 1 A, 2 B’s, 2 C’s, and 1 D. Since the puzzle also tells us we already know which cell contains the one D, we know the remaining five cells in row 1 must contain 1 A, 2 B’s, and 2 C’s.

Hint 2: We know from the rules two of the same letter cannot be next to each other. Therefore, we know the solution for the cells in row 1 cannot be “ABBCDC,” “BBACDC,” “BBCCDA,” “ACCBDB,” “CCABDB,” or “CCBBDA.”

Hint 3: What do we know about the content of column Q? We know from the puzzle, column Q cannot contain an A. We also know from the puzzle, row 6 contains three A’s. Based on Tip 2 (under the section titled, “General Tips for any 6 x 6 ABCD Puzzle”), we know one of the two last cells in row 6 MUST contain an A. If cell Q6 cannot contain an A then R6 must contain the A.

Hint 4: What do we know about the content of row 3? We know from the puzzle, column Q cannot contain an A. We also know from the puzzle, row 3 contains three A’s. Based on Tip 2 (under the section titled, “General Tips for any 6 x 6 ABCD Puzzle”), we know one of the two last cells in row 3 MUST contain an A. If cell Q3 cannot contain an A then R3 must contain the A.

Hint 5: What do we know about the content of cell Q5? The puzzle tells us the cell cannot contain any A’s or B’s. The fact there is a D next to Q5 tells us the cell cannot contain a D. There is only one letter that can be in the cell . . . .

Hint 6: You may not be able to solve the puzzle with only the previous five hints, but you have already solved approximately 1/3 of the puzzle and the remaining cells are solvable. The ABCD puzzle would not be a cognitive challenge if I provided all the hints or answers. Good luck.

**Variations**

You can find an example of some of the following variations here:

- Change the number of letters used – ABC, ABCD, ABCDE, etc.
- Supersize the grid – an ABCD puzzle could be any size
- Substitute letters for numbers in clues above and to the left of a grid
- Add a Rule – no letter can be diagonally adjacent to itself
- Eliminate cells from the grid
- Remove clues above and to the left of a grid

**Credit**

Click here to read another Beyond Injury post in the Torture or Teacher series.

Thanks to Barnes & Nobel for stocking the book in which the puzzle appears; Publications International for creating the example I used in this post, publishing a book that includes the puzzle, and allowing me to include the puzzle in this post; Puzzlewiki for providing examples of some puzzle variations; Google for helping me find the picture; and all the people who, directly or indirectly, made it possible for me to include the picture and text I used in this post.