Enter numbers from 1 to 9 into the cells of the pyramid, so that each number is either the sum or the difference of the two numbers in the cells below. In gray rows, no number may occur twice, while in white rows at least one number does occur twice.
(Rules and example from WPC 2018 IB)
- Range of numbers used may vary, as for example 0-9 Pyramid from WPC 2019/World Cup Round 2.
History of the puzzle
Earliest instance found is "Figure Pyramid" from "varia" round of 2003 Dutch Nationals. The puzzle was written by Hans Eendebak (Netherlands).