IBM Research | Ponder This | February 2015 challenges
Skip to main content

Ponder This

February 2015

<<January February March>>

Ponder This Challenge:

In continuation of last month's challenge: Find a uniquely solvable Kakuro, where for every square X and every two definitions there is a different value for those two definitions that gives at least one solution that differs from the original solution, for at least the square X.

Please supply the answer in the same format as last month's challenge.

Note that a solution for January's challenge does not necessarily solve this month's puzzle.

For example:

3 A1 A2
4 B1 B2
3 A1 B1
4 A2 B2

is not a valid solution, because when we ignore the first and last definitions, we still have only one possible value for B1: 1.

Update (02/08): Bonus '*' for a non rectangular Kakuro.

We will post the names of those who submit a correct, original solution! If you don't want your name posted then please include such a statement in your submission!

We invite visitors to our website to submit an elegant solution. Send your submission to the

If you have any problems you think we might enjoy, please send them in. All replies should be sent to:


Challenge: 01/29/2015 @ 12:00 PM EST
Solution: 03/02/2015 @ 12:00 PM EST
List Updated: 02/02/2015 @ 12:00 PM EST

People who answered correctly:

Franciraldo Cavalcante (01/30/2015 03:46 AM EDT)
Lorenz Reichel (01/30/2015 07:24 AM EDT)
William Heller (01/31/2015 01:25 AM EDT)
Oleg Vlasii (01/31/2015 09:47 AM EDT)
*Radu-Alexandru Todor (01/31/2015 11:47 PM EDT)
Dieter Beckerle (02/01/2015 05:20 AM EDT)
*Daniel Bitin (02/01/2015 03:46 PM EDT)
Armin Krauss (02/01/2015 07:42 PM EDT)
Emilio Del Tessandoro (02/02/2015 07:59 AM EDT)
Kang Jin Cho (02/02/2015 12:21 PM EDT)
Graham Hemsley (02/02/2015 01:38 PM EDT)
David Greer (02/03/2015 06:36 PM EDT)
*Motty Porat (02/04/2015 11:44 AM EDT)
*Donald Dodson (02/04/2015 06:06 PM EDT)
Liubing Yu (02/05/2015 02:27 AM EDT)
Chuck Carroll (02/05/2015 10:14 AM EDT)
*Joseph DeVincentis (02/05/2015 06:33 PM EDT)
*Mark Pervovskiy (02/07/2015 11:00 PM EDT)
*Armin Krauss (02/10/2015 03:50 PM EDT)
Lucas Mirelmann (02/10/2015 06:07 PM EDT)
Vladimir Dorofeev (02/13/2015 09:45 AM EDT)
*Franciraldo Cavalcante Jr (02/13/2015 04:40 PM EDT)
Shouky Dan & Tamir Ganor (02/16/2015 09:32 AM EDT)
Dan Ismailescu (02/16/2015 10:23 PM EDT)
Yujin Kim (02/17/2015 01:51 PM EDT)
Kwonil Kobe Ko (02/18/2015 10:32 PM EDT)
Yue Ru Sun (02/20/2015 09:42 PM EDT)
Peter C. Shim (02/21/2015 12:27 PM EDT)
Kyoung A. Lee (02/21/2015 03:35 PM EDT)
*Igor Novak (01/21/2015 07:45 PM EDT)
William Kang (02/22/2015 12:38 PM EDT)
Ji Eun (Grace) Kim (02/22/2015 02:53 PM EDT)
Chaeyeon Oh (02/22/2015 04:55 PM EDT)
Woosung Jung (02/25/2015 08:10 PM EDT)
*Li Li (02/28/2015 01:39 AM EDT)
Shirish Chinchalkar (02/28/2015 10:11 AM EDT)
Hyun Jae Moon (02/28/2015 11:17 AM EDT)
Robin Injoo Park (02/28/2015 04:03 PM EDT)
Daniel Hahn (02/28/2015 08:53 PM EDT)

Attention: If your name is posted here and you wish it removed please send email to the