Puzzle 1: Take a 4x4 grid of 0’s and replace ten of them with 1’s so that the sum of each row, column, and major diagonal* is an odd number.

Puzzle 2: The same as puzzle 1 with the rows, columns, and major diagonals each summing to an even number.

Bonus: Select your answers for puzzles 1 and 2 in such a way that the answer for Puzzle 1 can be changed to an answer for Puzzle 2 by moving the positions of just two of the 1’s.

* by “Major Diagonal” I mean one that starts in one corner of the grid and ends in the opposite corner. There are two major diagonals.

1. dan (solved: 6:05am 2-14-2005)
2. Jonathan (solved: 9:25am 2-14-2005)
3. The Killer Llama (solved: 11:21am 2-14-2005)
4. Kimberly McGraw (solved: 3:42pm 2-14-2005)
5. the greathoj (solved: 3:49pm 2-14-2005)
6. nonr (solved: 7:41pm 2-14-2005) *
7. tom von kercey (solved: 12:43am 2-15-2005)
8. Sriram (solved: 9:24am 2-15-2005)
9. eeyalpud ydna (solved: 11:54am 2-15-2005)
10. bluedragon0583 (solved: 8:37pm 2-15-2005)
11. Erin (solved: 10:24am 2-16-2005)
12. none (solved: 10:44am 2-16-2005) *
13. Rachel (solved: 12:53pm 2-16-2005)
14. Josh Giedeman (solved: 8:08pm 2-16-2005)