My 9 year old is in 3rd grade and he really struggles with math. I have never been a math scholar myself. I did OK, but never great and I got a lot of help from my dad who is a math wiz. My son only has me to help him and I am no math wiz. Since my son struggles I know that what might be obvious to me may not be obvious to him and I have to be very careful and clear about how I explain things to him, and many times I have to change my thinking to re-explain things to him in a way that he understands. His class just finished a unit on shapes. 2-Dimensional and 3-Dimensional Shapes to be exact. For those of you who have 3rd graders or any grade level of children studying these shapes I am going to try to simplify the explanation for you.
2 Dimensional Shapes
A 2-Dimensional shape is by definition: A shape whose points are all in one plane. OK most kids would hear that and go "WHAT?" Basically it means a shape that is flat. So while the shape will have length (the measurement side to side) and width (the measurement from top to bottom) it will not have any thickness. It is flat. So all of your basic shapes including your squares, triangles, rectangles and even circles are all 2 dimensional shapes.
Think about a regular 2D movie, it is shown on a flat screen, the characters, nor the scenery, nor the props pop out at you. In your home or at school a piece of paper would be considered a 2 D shape because it has length and width but it is flat it has no thickness. A poster is another good example, even a towel, or a flat bed sheet would be examples of 2-Dimensional shapes.
Pretty easy huh?
Now 3-Dimensional Shapes are a little bit more difficult to explain and a little more interesting to look at.