simple arithmetic mean

例句：

1. 1. The simple design of the house is very appealing.
   房子的简单设计非常吸引人。
2. 2. He explained the problem with simplicity.
   他以简单的方式解释了这个问题。
3. 3.The teacher asked the students to work on a simple project.
   老师要求学生们做一个简单的项目。