Composing and Decomposing 2-D Shapes (Grade K) | 拼搭与拆分二维图形（K年级）

📚 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。

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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