Monday, January 28, 2013

Nets of 3D figures

Nets are always a great way to help the students see what the 3D figure looks like.  The most difficult thing for them to grasp is that the base is not always what the figure is sittting on.  With this hands on activity, the kids are able to see the 2D form and then actually fold it into the 3D figure.

I gave the kids 5 nets:

  • rectangular prism
  • Triangular prism
  • Triangular Pyramid
  • Square Pyramid
  • Cylinder

I have copies from an old textbook, but I have found some on the internet that work, as well.
Here is one site:

This year, I had the kids follow these steps:

  1. Sketch the net
  2. Identify the figure
  3. Identify the shape of the base
  4. Calculate the area of each base and face (use the actual net; NOT your sketch)
  5. Measure in cm
  6. Round to the nearest half cm
  7. You may use a calculator
  8. For the cylinder net, the rectangle part does not stay a rectangle; therefore, you cannot use lw for that part. It curves around, so for that part, you use: 2(pi)(r)(h)
  9. Calculate the height of the figure
We made 2d and 3d books, so they include the sketches and the information above in the back of that book.

After writing the above information, I also had the kids do the following to the actual net:
  • Color the base(s) of the figure
  • Cut the net out - Do NOT cut the tabs off
  • Fold the net and create the figure
  • Use GLUE
  • Create a mobile, by taping yarn to each figure

We hung the models from the ceiling.

As I was walking around the room, I would talk to them about what the base was.  Many of them still wanted to say the rectangle was the base of the triangular prism.  After I stood the prism up on the triangle, they were able to see that you could put it on any of the sides.  I hope it helped!

I had the kids in cooperative learning groups.  Phew!  I am worn out from all the same questions.  It is amazing since I:
  • Verbally gave instructions
  • Posted the instructions on the screen
  • Printed out instructions for each group

They don't take the time to READ.  Tomorrow, I have printed off a following directions test.  I cannot handle another day like Friday and today!  It is exhausting to say the same thing over and over.

I want to keep group work with the hands-on activities, so hopefully, the kids will learn better habits.

Here is a FREE copy of the posted and printed instructions I gave the kids.  

Happy net folding!

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