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Math Mammoth 3A and 3B Question - no 2-digit mult


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Yikes. I am wondering if I am missing something. My son is doing area and perimeter in MM 3-B, but to do that he needs to know how to do 2-digit multiplication. I am looking back at the 2 multiplication chapters in 3-A and not seeing it either. So, I am just helping him along with the area and perimeter problems as he needs it. Now I am also wondering shouldn't this have been in a 3rd grade math curriculum. I have loved this curriculum, but I am a little concerned that this is missing and wondering if we have missed anything else. Has anyone addressed this before? Thanks!

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I'm trying to remember right now, but isn't the idea to draw lines and cut the shape into blocks, then count the number of blocks of area?

 

Imagine a square that's 2 units on a side, divided into 4 smaller squares. You would count the smaller squares to get the area.

 

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We are finishing up MM3 next week for the year and it was not covered. When problems arose that had 2 digit multiplication I showed her how to do it on the fly. I figured it was in MM4, but I have not looked yet.

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If it is squares and rectangles, can you not use repeated addition?

 

Pretty sure we did that. I don't recall.

 

MM does have them kind of dabble in concepts in a roundabout way before they're taught from time to time. They do have the information needed to figure it out, but if you expect the standard algorithm to be taught first every time a concept shows up, you might get annoyed a lot. :001_smile:

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The lesson is "More Area and Perimeter" on p. 74-75 of 3B. The multiplication is simple enough that I was able to talk him through it. (ex. 30 X 9) Or, like someone mentioned, we could have used repeated addition. I think it surprised me that it wasn't in the 3rd grade curriculum at all though once I started looking. I did see on her website where she outlines places where MM doesn't line up with CA state standards, and that is one of them. I really appreciate the thorough understanding that they get if the concepts in MM, so I don't think I would have chosen differently. I might just pay more attention from now on to places where it deviates from the standards, because that is important to us. Thanks for the feedback.

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I don't have the latest version, so my 3B doesn't have the section you're talking about, but the area calculated in my 3B has you counting boxes rather than multiplying. Has yours actually taught area as multiplication yet? I remember hitting that section, and my son realized he could multiply instead of counting boxes, so we multiplied, but it wasn't actually taught that way until the grade 4 books, I thnk.

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The lesson is "More Area and Perimeter" on p. 74-75 of 3B. The multiplication is simple enough that I was able to talk him through it. (ex. 30 X 9) Or, like someone mentioned, we could have used repeated addition. I think it surprised me that it wasn't in the 3rd grade curriculum at all though once I started looking. I did see on her website where she outlines places where MM doesn't line up with CA state standards, and that is one of them. I really appreciate the thorough understanding that they get if the concepts in MM, so I don't think I would have chosen differently. I might just pay more attention from now on to places where it deviates from the standards, because that is important to us. Thanks for the feedback.

This is taught on page 65-67. HTH!

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