Dear Eva,
I would like to help you out with the check numbers since they are so much fun once you learn about them. i would also point you to the games book where they are explained in detail with examples if you still don't get it from my description.

The idea of check numbers works because we have a limited number of digits to work with, though joan tells us they will work with any base system and i believe her, it is just harder to picture that way. So, the first thing you want to do is look for nines and cross them out because 9=0. Every other number is added together to form the check number for that line. for instance; 3,479 - 1,299=2,180 The first number gets the 9 crossed out, then add 3 + 4+7=14 Add the two digits together to form 5 as the check number. The second number you cross out the 9s and it leaves 3 as the check number. The answer you can cross out the one and eight because they make 9 which leaves a 2 for your check number. So 5-3=2 so you know your answer is right. Or you could say 2 +3=5 by adding the last two to get the first one. That is often necessary in subtracting.

Now, why does it work? For an easy explanation try to draw a table with the numbers lined up.
1 2 3 4 5 6 7 8 9=0
10=1,11=2, 12=2, 12=4, 14=4, 15=6, 16-7, 17=9, 18-9=0
19=10=1, etc

You can see that every number would fit into the pattern, so the number 2456 for instance would be 2+4+5+6 or 17=8 [you could have cast out the 5,4 for a 9 and added the 2 and 6 to get the 8 too] Either way it always works.

I hope that helps. The joy is it will work for adding, subtracting, multiplying and dividing so once you learn it you have a ready tool to check all your calculations and you are empowered to know you are right.
Nancy

Dear Eva,
Just a couple more things regarding check numbers. The game number for this skill is A63 and it is also explained step by step in the D level lessons 47, 49, & 50. Also, if you still want more help, just do a search at the top of the page on the forum for check numbers and you will see lots of other posts that may help make it even more clear for you. Sometimes the way one person explains it seems more clear than another. It also shows you that you are not the only person who doesn't get this skill. it takes time and effort at first but it unlocks so much once it is mastered.
Nancy

We just hit lesson 47 in Level D as well, and my mind boggled.

I saw that it was covered in the lessons ahead, so I expect I'll pull it together. My first response was why do it, if we need a chart, etc., but I looked ahead, and looked here. I trust it will become easier and more natural to use, and help my daughter check her work (she has an unhappy habit of mixing addition and subtraction without caring whether answers make any sense, I'm afraid).

I would, however, respectfully suggest that it might be nice to include a note for parents in Lesson 47 that helps guide US through the process, or reassure us that further explanation lies ahead. Just a bit more in the scripting would stave off parental anxiety at this point, I believe. Thanks, as always!

Kristina

Dear Kristina,

I will mention your suggestion at our next company meeting, as to adding a note to partents that they will be further explaing chck numbers in the next few lessons.

Please let me know if you have any more questions. You can email me directly at Carissa@alabacus.com .

Thank you for giving your child a RightStart in Math,

Carissa
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