# Concepts in Action: Equivalence between the trapezoid and T2

From wikisori

## Contents

### Age

6-9.

### Materials

- From the triangular box: grey equilateral triangle
- From the small hexagonal box: yellow equilateral, three green equilateral triangles

### Preparation

### Presentation

- Unite the three green triangles to form a trapezoid.
- Knowing that each of these small triangles is congruent to the red triangle having the value of 1/4 T1, we can say that the trapezoid has the value of 3/4 T1.
- The trapezoid can be superimposed on the grey equilateral triangle to show that 1/4 is lacking.
- We've already seen that the red obtuse-angled triangle was equivalent to the small red equilateral triangle having the value of 1/4 T1.
- So each green triangle would also be equivalent to a red obtuse-angled triangle.
- These obtuse-angled triangles were each 1/3 of T2; T2 is composed of three obtuse-angled triangles having the value of 1/4 T1.
- Therefore T2 is equal to 3/4 T1.
- Having the same value of 3/4 T1, the trapezoid and T2 are equivalent.

### Control Of Error

### Points Of Interest

### Purpose

### Variation

### Links

### Handouts/Attachments