ABSTRACT
Th e square grid is a multiplication table. Each number is the product of the respective row and column numbers. Th e missing number is 9.
To exchange the knights you will need the 11 moves listed:
1. b-j-e 7. a-c-j 2. d-b-j 8. i-a-c 3. f-d-b 9. g-i-a 4. h-f-d 10. e-g-i 5. j-f-h 11. j-e-g 6. c-j-f
