Frequently Asked Questions

Q1. So many possible values! How do I start?

Remember, no zeroes, and no digit is repeated within a sum. First, see the instructions. This should get you started. Then read up on the advanced techniques before tackling harder puzzles.

Q2. I think the puzzle has an error and cannot be solved.
Q3. I think the puzzle has more than one solution.

Respectfully, I must assure that you are wrong. So far, my puzzles have all been 100% airtight! However, a simple arithmetic mistake you make in one place might cause a contradiction or ambiguity several squares away! I suggest you check again, or press the "Check Answers" button - any square in which you have placed an incorrect value will be highlighted in red. Fixing the highlighted squares will get you back on the right road.

Q4. It seems like I need to guess. Is that right?

You may need to use a little trial-and-error sometimes. Generally, if your guess is wrong, it leads to a contradiction within several moves.

Q5. I'm stuck. Can you help me?

Unfortunately, I cannot help individual players - there are not enough email minutes in the day!

My best advice is to keep trying. Check out the instructions and advanced tutorial. Like many things is life, practice makes perfect.

Q6. These are fun! Where can I get more?

Please consider one of the items in our books link. There are also free puzzles at:

Q7. I run a website/newspaper/magazine that would like to include your cross sum puzzles.

Let's talk! Email me.

Q8. I am a teacher. Can I use these puzzles in my classroom?

I have some small, simple 9x9 puzzles that might be very useful for practing arithmetic skills. Email me.

Q9. I love your site. Can I help keep it running by making a donation?

Thanks! My plan is to keep it free for as long as I can. The best way to support me is to buy a book but a small donation is always welcome. Please use the link here: