# Question for Singapore Users: Need a supplement for addition and subtraction 2B

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Hi Everyone,

My daughter has hit a road block in math.   We are working through Singapore 2B (standard) and I noticed that she was getting nearly every problem wrong when we got to the money unit.   I was having her re-work the problems when she would miss them, but she just wasn't getting it.    We worked through every problem in the workbook and textbook and she is still missing a lot of the problems.  She can do fine when she stacks the number, but Singapore really wants the child to mentally manipulate the numbers.

After going back and reviewing for awhile, I have realized that her understanding of addition and subtraction (specifically 3 digit mental math strategies) is not as strong as it should be.   I think that is what is causing her problems with the money problems.  Makes sense, right?

SO---I need a new way to teach these mental math concepts.  Any suggestions?

I was thinking of ordering one of the math mammoth addition/subtraction worktexts to supplement, but I am not sure which book to order.   What would be the equivalent of what is covered in Singapore 2B??   I was thinking the MM Add & Subtract grade 3, but I want to get confirmation before I buy.

OR--would I be better off ordering one of the Singapore books?  Intensive practice, extra practice, etc. etc.

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I've only used up to 2B myself, which does thorough mental work with two-digit numbers. If you're looking for three-digit, I think book 3 is the right choice. Perhaps you could email the author? She's generally very responsive.

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We are using the 2A and 2B Intensive Practice to supplement Miquon. Let me whip them out...

2A

Topic 1: Numbers to 1000, which deals with place value and number sense. Indirectly related.

Topic 2: 1 page each on addition without renaming, subtraction w/o renaming, addition with renaming, and subtraction with renaming. Number bonds and bar model representations. Some different problems, such 298 + 606 = 400 + ____. Word problems that step you through bar models.

Topic 3: Length--measuring and drawing lines. Word problems with length that can incorporate the mental math strategies.

Topic 4: Weight with word problems that can incorporate mental math strategies.

Topics 5 and 6: Multiplication

2B

Topic 1: Entirely mental addition and subtraction with coaching in the strategies and lots of practice. It includes word problems.

Topic 2: Multiplication and Division

Topic 3: Money--this includes opportunities for mental math.

Topic 4: Fractions

Topic 5: Time, including elapsed time.

Topic 6: Capacity, which uses whole numbers and fractions.

Topic 7: Graphs

Topic 8: Geometry

Topic 9: Shapes and Patterns

Both books have a review section. If I didn't talk about mental math, that section doesn't include a substantive amount of mental math.

I have not seen the extra practice for level 2, but based on level 3, it probably has some mental math in it. We start Singapore around level 3.

HTH helps you compare.

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My thought is that mental math comes with practice.  I talk about the mental math way to do everything, but let my children do the math in the way that makes them the most comfortable. We've done singapore for a long time and they all eventually get it.

If it really bothers you, what about making a "warm up" problem before every lesson and keep practicing the mental math.  But my experience says that might just make the kid hate that type of math and shut down.  You might just want to lay it aside and revisit it again when mental math comes up with the thousands place in 3A.  You know your kid best!

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Have you used the mental math exercises in the back of the teacher's manual? Beyond those, Challenging Word Problems 2 has a chapter devoted to mental calculations. I'll pull from one of those two sources almost every day and have DD start math with a mix of 6-10 addition/subtraction facts.

Beyond that, my daughter loves the Flash Kids Problem Solving books. The books themselves are cheap, colorful, and engaging, and the problems lend themselves beautifully to mental math strategies. We do level up in them. (DD1 did the third grade book with Primary Mathematics 2A and will do the 4th grade book with 2B.)

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SO---I need a new way to teach these mental math concepts.  Any suggestions?

The best way to teach the mental math concepts in Singapore Math, IMO, is to do the suggested games and activities in the mental math sections of the Home Instructor Guides.  Have you already tried any of those?

We played a variety of mental math games using a couple of 10-sided dice.

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Take a look at Developmental Math each book is one topic and can be completed in a few weeks. I've never done the hundreds/ thousands book but the strategies helped my DS a lot with 2 digit mental concepts (making 10's, breaking apart numbers etc...) I'm guessing you'd look at level 10 or 11- there are some samples on Christian Book  think RR has them also. They look really simply but have helped my dc's tremendously to solidify their skills. I've only used it as a supplement and never used the TM

ETA - be sure to read the table of contents to get an idea of what's in the book - the samples are not wholly representative.

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I second the recommendation for the dice games that are in the HIG for 2B. My son has gotten much better at mental math with those, especially learning to use the near-hundred and near-fifty amounts to do his calculations more quickly.

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If you aren't already using the Mental Math and additional games in the Singapore HIGs, I recommend starting there. I found that ten Mental Math questions daily made a significant difference in keeping mental math skills sharp.

If the difficulty actually lies in understanding of place value and regrouping, you could give a daily warm-up of a couple of three-digit addition or subtraction problems and talk through the mental math strategies for approaching them. Begin by reviewing what each digit of each number represents, using manipulatives if you have them. (I used c-rods and Base-10 hundreds for this.) Work the problems out with manipulatives, and then in writing. Doing this every single day feels slow and redundant, but I've found it incredibly effective.

I also use the CWP and Intensive Practice books, lagged a bit, to provide some ongoing review. (I'm sure MM could work equally well.) I would avoid Singapore's Extra Practice books in this case, as they provide minimal extra practice at a simpler level than the workbook for every topic in a semester.

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