# Constructive Triangles: First Box

## Contents

6-9.

### Materials

Box 1-

• Two yellow equilateral triangles
• Two yellow, two green right-angled isosceles triangles
• Two yellow, two green, two gray right-angled scalene triangles
• One red smaller right-angled scalene triangle
• On red obtuse-angled scalene triangle
(Each triangle has a black line along one side)

### Presentation

1. Invite the child to remove the triangles from the box, and then sort the triangles according to shape.
2. Having done this, ask the child to separate each pile according to color, resulting in various piles of triangles having both shape and color in common.
3. Isolate the two red ones to be used later.
4. The directress takes the pile of two equilaterals and separates them in such a way that the two black lines are facing each other.
5. Watch, these black lines are like a magnet.
6. Slide the two triangles together so that the black lines meet.
7. Invite the child to do the same, leaving the joined triangles in place.
8. Identify the figures that have been constructed: a yellow rhombus, a green square, and a gray rectangle.
9. The directress identifies the other three figures as common parallelograms (parallelogram: Greek parallelogramium <parallelos, parallel, and grame, figure>).
10.  Therefore a parallelogram is a plane figure having parallel sides.
11. By simultaneously running two fingers along two parallel sides, the directress gives a sensorial impression of parallel.
12. We also call them common parallelograms to differentiate them from the square, rectangle, and rhombus which could also be considered parallelograms.
13. The child names each figure as they are indicated by the directress.