📚 Building with Shapes: Compose and Decompose | 用图形拼搭：图形组合与拆分
Welcome to Lesson 15-8! In this lesson, you will learn how to put shapes together to make new shapes, and how to take big shapes apart into smaller parts.
欢迎来到第15章第8课！在这节课中，你将学习如何把图形拼在一起组成新图形，以及如何把大图形拆成较小的部分。
1. Learning Goals | 学习目标
I can name basic two-dimensional shapes.
我能说出基本二维图形的名称。
I can combine smaller shapes to make a larger shape.
我能把较小的图形组合成一个较大的图形。
I can take a larger shape apart into smaller shapes.
我能把较大的图形拆分成较小的图形。
2. Shape Vocabulary | 图形词汇
Let us review the names of the shapes we will use today.
让我们复习今天要用到的图形名称。
| Shape | 图形 | Sides | 边 | Corners | 角 | Symbol | 符号 |
| Circle | 圆形 | 0 | 0 | ○ |
| Square | 正方形 | 4 | 4 | □ |
| Triangle | 三角形 | 3 | 3 | △ |
| Rectangle | 长方形 | 4 | 4 | ▭ |
| Hexagon | 六边形 | 6 | 6 | ⬡ |
3. What Does "Compose" Mean? | “组合”是什么意思？
To compose means to put parts together. When we compose a shape, we join smaller shapes to make one larger shape.
组合就是把各个部分拼在一起。当我们组合一个图形时，我们把较小的图形连接起来，组成一个较大的图形。
For example, two squares can be placed beside each other to make a rectangle.
例如，两个正方形并排放在一起，可以组成一个长方形。
4. Triangles Make a Rectangle | 三角形拼成长方形
Take two identical right triangles and place them along their longest side. The two triangles join perfectly to form a rectangle.
取两个完全相同的直角三角形，把它们最长的那条边拼在一起。这两个三角形就能完美地组成一个长方形。
△ + △ = ▭
Notice that the rectangle has 4 sides and 4 corners, while each triangle has 3 sides and 3 corners.
注意，长方形有4条边和4个角，而每个三角形有3条边和3个角。
5. Four Squares Make a Big Square | 四个正方形拼成一个大正方形
Place four congruent squares in a 2-by-2 grid. They form one larger square.
把四个大小相同的正方形排成2行2列。它们就组成了一个大正方形。
□ + □ + □ + □ = □
We can also write this as a multiplication equation: 2 × 2 = 4.
我们也可以把它写成乘法算式：2 × 2 = 4。
6. Six Triangles Make a Hexagon | 六个三角形拼成六边形
Six congruent equilateral triangles can be arranged around a point to make a regular hexagon.
六个完全相同的等边三角形围绕一个点排列，可以组成一个正六边形。
△ + △ + △ +
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