Killer Soduku Math Error

 Thu Dec 16, 2021, last updated Wed Jun 08, 2022 -  Jim Deibele

So my daughter Charlotte introduced me to Killer Soduku, an IOS app that makes it a little easier to solve soduku problems by giving you hints on what certain boxes should add up to.

The other day I was sure I knew what most go in a box but Soduku gave me a red square indicating that 9 was not the right answer. I went on to solve the puzzle except for that square. As you can see, Killer Soduku says the last digit left to be used (on the lower right) should be 8. But 4+2+9+7 = 22. If the total is 31, the answer must be 9, not 8.