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11-28.

Multiple Choice: Which net below cannot create a regular octahedron when folded, like the one directly at right?  

Octahedron with all triangular faces.

  1. A net of 8 equilateral triangles, alternating up & down, to share a side, across rows, and between rows, arranged in 4 rows, with 6 possible positions from left to right as follows: Row 1: third, up, Row 2: third, down, fourth, up, fifth, down. Row 3: first, up, second, down, third, up. Row 4: third, down.

  1. A net of 8 equilateral triangles alternating up & down to share a side, across rows, and between rows, arranged in 4 rows, with 4 possible positions from left to right as follows: Row 1: second, up, Row 2: first, up, second, down, third, up, fourth, down. Row 3: third, down, fourth, up. Row 4: fourth, down.

  1. A net of 8 equilateral triangles alternating up & down to share a side, across rows, and between rows, arranged in 4 rows, with 3 possible positions from left to right as follows: Row 1: first, up, Row 2: first, down, second, up, third, down. Row 3: first, up, second, down, third, up. Row 4: first, down.

  1. A net of 8 equilateral triangles alternating up & down to share a side, across rows, and between rows, arranged in 3 rows, with 4 possible positions from left to right as follows: Row 1: second, up, Row 2: first, up, second, down, third, up, fourth, down. Row 3: first, down, third, down, fourth, up.

  1. None of these

Try to locate the edges which will match up to form half the shape.

For example, in the net for part (a):

A net that folds into an octahedron. The two center sides fold together. Then the side flaps fold up.

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