Lesson 3: Midpoint - Midpoint of 3D Objects

   Constructing Knowledge

Finding the midpoint of a 3-D object is similar to finding the midpoint of a 2-D shape.

As a general rule, to find the midpoint of any 3-D object:

  1. Find the midpoint of each face.

  2. For objects with an even number of faces, connect the midpoint of one face to the midpoint of the opposite face (example: front to back or top to bottom)
    or
    For objects with an odd number of faces: connect the midpoint of one face to the opposite vertex.

The midpoint of the object is where the lines intersect.

   Multimedia

A video demonstrating finding the midpoint of a prism is provided.



EXAMPLE 1

Find the midpoint of the rectangular prism using a ruler and pencil.



Solution


Step 1: Find the midpoint of each face.

In this example diagonals are drawn to find the midpoint of each face.







Step 2. Connect the midpoint of each face to the midpoint of the opposite face.



The midpoint of the prism is where the lines intersect.


Now, it is your turn! Complete the questions in your Chapter 6, Lesson 3 Practice Makes Perfect that refer to Midpoint of 3D Shapes.



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