Fill in gaps when changing math programs, 4th grade

[Janeway]

We have done Singapore Math. But I always liked BJU so after daughter was done with Singapore Math 2B, we did BJU grade 3. We used real Singapore Math, US edition and she used MIF in her charter school. So even though she had through 2A of MIF, she still had to back up and do 2A of primary maths, US edition. Now, after finishing grade 3 of BJU, we agreed to return to Singapore Math (it was never broken, we liked it, it is just BJU is great too). She is the one who asked to switch back to Singapore Math. However, on the placement exam, she passed out of 3B, but has missed multiplication with longer numbers from 3A. I do not want to do the entire book of 3A over a missed unit or two. I have the textbook and workbook though. IF we were to continue with BJU, these concepts are in BJU 4th grade. They are also in 4th grade Math Mammoth. I see Math Mammoth has topical books on the subject. Kumon does too. The other option is to just use the Singapore math textbook and workbook I have now and just not let her write in the workbook. Our intent will be to continue with Singapore Math,  Primary, US edition after. 

[countrymum]

I'd fill in with singapore math as that is where your headed. I've been doing a very simular thing with son as we move from RightStart to math mammoth for 5th grade. Except as were moving to math mammoth, we are filling in with math mammoth. That seems to make the most seemless transition. They are then used to the types of problems and layout also.