An envelope is drawn with one flap from the top corners down to the middle of the bottom edge and another from the bottom corners up to the middle of the top edge. How many triangles are there?

Question

Accepted Answer

12. Smallest: 3 on each side (top, outer, bottom of each crossing point), 6. Two-piece triangles that have the left or right edge as a side: 2 on each side, 4. Big triangles, each a whole flap: 2. Total 6 + 4 + 2 = 12 .

An envelope is drawn with one flap from the top corners down to the middle of the bottom edge and another from the bottom corners up to the middle of the top edge. How many triangles are there?

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