Thursday 31 October 2019

IBM Ponder This Challenge April 2019

IBM do  very nice monthly challenge called IBM Ponder This:
http://www.research.ibm.com/haifa/ponderthis/challenges/April2019.html

This months Challenge is from Reda Kebbaj is :
"Find nine different prime numbers that can be placed in a 3x3 square in such a way that the average of every row, column, and diagonal is also a prime number."

I tried randomly trying different primes but eventually gave up and resorted to some programming. The smallest prime to make this work is a 59.
3x3 Array:
5, 11, 17 = 11
23, 29, 59 = 37
41, 47, 53 = 47
--  --  --
23, 29, 43
3x3 Array:
5, 11, 17 = 11
41, 47, 53 = 47
23, 29, 59 = 37
--  --  --
23, 29, 43
3x3 Array:
5, 11, 41 = 19
17, 23, 29 = 23
47, 53, 59 = 53
--  --  --
23, 29, 43
3x3 Array:
5, 11, 41 = 19
47, 53, 59 = 53
17, 23, 29 = 23
--  --  --
23, 29, 43
3x3 Array:
5, 17, 29 = 17
41, 47, 53 = 47
11, 23, 59 = 31
--  --  --
19, 29, 47
3x3 Array:
5, 23, 29 = 19
41, 47, 53 = 47
11, 17, 59 = 29
--  --  --
19, 29, 47
3x3 Array:
5, 23, 59 = 29
17, 41, 53 = 37
11, 29, 47 = 29
--  --  --
11, 31, 53
3x3 Array:
5, 29, 53 = 29
11, 17, 59 = 29
23, 41, 47 = 37
--  --  --
13, 29, 53
3x3 Array:
5, 29, 53 = 29
11, 41, 59 = 37
17, 23, 47 = 29
--  --  --
11, 31, 53
3x3 Array:
5, 29, 53 = 29
17, 23, 47 = 29
11, 41, 59 = 37
--  --  --
11, 31, 53