📚 Composing and Decomposing 2-D Shapes (Grade K) | 拼搭与拆分二维图形（K年级）
Welcome to Lesson 15-9! In this lesson, we will explore flat shapes, such as triangles, squares, rectangles, and hexagons. We will learn two powerful ideas: composing, which means putting shapes together to make a new shape, and decomposing, which means taking a big shape apart to find smaller shapes inside.
欢迎来到第15课第9节！在本课中，我们将探索平面图形，例如三角形、正方形、长方形和六边形。我们将学习两个重要的概念："拼搭"，也就是把图形放在一起组成一个新图形；以及"拆分"，也就是把一个大图形拆开，找出里面的小图形。
Composing and decomposing help us see the world like a puzzle. When you look at a window, a door, or a picture, you can find many simple shapes inside. By the end of this lesson, you will be able to put shapes together and take them apart with confidence.
拼搭和拆分会帮助我们像看拼图一样看世界。当你看到窗户、门或一幅画时，你可以在里面找到许多简单的图形。学完这节课后，你将能够自信地把图形拼在一起，并把它们拆开。
1. Flat Shapes We Know | 我们认识的平面图形
Flat shapes are two-dimensional (2-D) shapes. They have sides and corners, but they do not stick out like boxes. Here are some flat shapes we use in this lesson.
平面图形是二维（2-D）图形。它们有边和角，但不像盒子那样凸出来。以下是我们这节课会用到的一些平面图形。
- Triangle: a shape with 3 straight sides and 3 corners.
三角形：有3条直边和3个角的图形。 - Square: a shape with 4 equal straight sides and 4 corners.
正方形：有4条相等的直边和4个角的图形。 - Rectangle: a shape with 4 straight sides, 2 long and 2 short, and 4 corners.
长方形：有4条直边（2条长边、2条短边）和4个角的图形。 - Hexagon: a shape with 6 straight sides and 6 corners.
六边形：有6条直边和6个角的图形。 - Circle: a round flat shape with no straight sides and no corners.
圆形：没有直边、没有角的圆圆的平面图形。
Each shape has a special name. We can count the sides and the corners to tell one shape from another. Let us practice counting together.
每个图形都有一个特别的名字。我们可以通过数边和角来区分不同的图形。让我们一起数一数。
| Shape 图形 | Sides 边 | Corners 角 |
| Triangle 三角形 | 3 | 3 |
| Square 正方形 | 4 | 4 |
| Rectangle 长方形 | 4 | 4 |
| Hexagon 六边形 | 6 | 6 |
| Circle 圆形 | 0 straight sides 0条直边 | 0 |
Which shape has the most sides? Yes, the hexagon has 6 sides. Which shape has no straight sides? Yes, the circle has no straight sides.
哪个图形的边最多？是的，六边形有6条边。哪个图形没有直边？是的，圆形没有直边。
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