# Constructive Triangles: First Box

From wikisori

## Contents

### Age

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)

### Preparation

### Presentation

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

### Control Of Error

### Points Of Interest

### Purpose

### Variation