第五单元

Unit five

Focus on the Environment -- Addition and Subtraction of Fractions (2)

(关注环境——分数加减法（二）)

Lesson one

1. A city in the implementation of "garbage classification" project on the kinds of household garbage statistics.

某市在实施“垃圾分类”工程中对生活垃圾种类进行了统计。

2. One eighth of them are plastic, two fifths are vegetable peel, two fifths are waste paper, and one quarter is glass.

其中塑料占八分之一，菜叶果皮占五分之二，废纸占二十五分之二，玻璃占二十五分之一。

3. The plastic in living rubbish and vegetable leaf pericarp, which kind is much?

生活垃圾中塑料和菜叶果皮，哪类多？

4. How do you compare fractions with different denominators like this?

像这样分母不同的分数，怎么比较大小呢？

5. Let's compare it to a decimal.

化成小数来比较。

6. Compare them by converting them into fractions with the same denominator.

把它们化成分母相同的分数来比较。

7. What is a universal score?

什么叫作通分？

8. What is the common denominator?

什么是公分母？

9. Do you know how to score? Try to practice.

你会通分吗，试着练习一下。

10. I take the common multiples of 4 and 6 as the common denominator, and I rewrite them as fractions with the same components but the same magnitude.

我用4和6的公倍数作公分母，把它们改写成分母相同而大小不变的分数。

11. I use the least common multiple of 4 and 6 as the common denominator...

我用4和6的最小公倍数作公分母……

12. If you think about it, which number is easier to use as the common denominator?

想一想，通分时，用哪个数作公分母比较简便？

Lesson two

1. What percentage of the total number of days in a month are the air quality rated as excellent or good?

空气质量等级为优和良的天数一共占全月天数的几分之几？

2. What if the denominators are different?

分母不同怎么办呢？

3. Think about it. What do the two methods have in common?

想一想，两种方法有什么相同之处？

4. What percentage of the total number of days with good air quality grade are more than those with light pollution?

空气质量等级为良的天数比轻微污染的天数多占全月天数的几分之几？

5. Think about it. How do you add and subtract fractions of different denominators?

想一想，怎样计算异分母分数加减法？

Lesson three

1. China last year part of the city traffic noise pollution monitoring results statistical table.

我国去年部分城市交通噪音污染监测结果统计表。

2. What percentage of the cities monitored are polluted by traffic noise?

受交通噪音污染的城市一共占被监测城市的几分之几？

3. The noise affecting urban environment mainly includes living noise and traffic noise.

影响城市环境的噪音主要有生活噪音和交通噪音。

4. According to statistics, living noise in a city accounts for one half and traffic noise accounts for one third.

据统计，某城市生活噪音占二分之一，交通噪音占三分之一。

5. What is the proportion of other noise that affects the urban environment?

影响城市环境的其他噪音占几分之几？

Lesson four

1. From four students, xiaoli, xiao-jun, xiao-jie and xiao-yang, two students are selected to participate in the "children's drama competition" on behalf of our school. How many different combination methods are there?

从小丽、小军、小杰、小阳4名同学中，选出2人代表学校参加“少儿戏曲大赛”，有多少种不同的组合方法？

2. How do you find all the combinations in order?

怎样有序地找出所有的组合方法呢？

3. If 2 of the 5 students are selected to represent the school in the "Children's Drama Competition", how many different ways are there to form a team?

如果从5名同学中选出2人代表学校参加“少儿戏曲大赛”，有多少种不同的组队方法？

4. If the number of students is represented by a dot, and the line between two points is a method of forming a team, can you complete the following table?

如果用点来表示学生人数，用两点之间的线段表示一种组队方法，你能完成下表吗？

5. What patterns do you see?

从中你发现了什么规律？