第四单元

Lesson 4

Cloth Art Fun Group makes a batch of hats out of 6 meters of cloth. Each hat is made of 2/5 meters of cloth. Give two thirds of these hats to the kindergarten.

布艺兴趣小组用6米布制作一批帽子，每顶帽子用布2/5米。将这些帽子的2/3送给幼儿园。

What questions can you ask?

你能提出什么问题？

Cooperative exploration

合作探索

1. How many hats are given to the kindergarten?

1. 送给幼儿园多少顶帽子？

First how many hats have you made.

先求一共制作了多少顶帽子。

Then how many hats can I give to the kindergarten.

再求送给幼儿园多少顶帽子。

You can give a comprehensive solution.

可以列综合算式解答。

Six divided by two fifth times two thirds equals to ten(tops)

6÷2/5×2/3＝10(顶)

Answer: 10 hats for the kindergarten.

答：送给幼儿园10顶帽子。

Unit 4

The mysteries of the human body -- ratio

四 人体的奥秘——比

Lesson 1

Head length: twenty five cm

头部长：25㎝

Body length: 160cm

身长：160㎝

Leg length: 88cm

腿长：88㎝

Arm length：66cm

臂长：66㎝

What questions can you ask?

你能提出什么问题？

Cooperative exploration

合作探索

1. What is the relationship between the length of Zhao Fan's head and his legs?

1. 赵凡的头部长和腿长有怎样的关系呢？

You can use 25÷160 to show what fraction of the length of the head is.

可以用25÷160表示头部长是身长的几分之几。

It can be expressed as 160÷25 the body is several times the length of the head.

可以用160÷25表示身长是头部长的几倍。

The relationship between head minister and body length can also be said:

头部长和身长的关系还可以说成：

The ratio of the head to the length of the body is 25 to 160, denoted as: 25:160 or 25/160;

头部长和身长的比是25比160，记作25：160 或25/160:；

The ratio of the length of the body to the length of the head is 160 to 25, called 166:25 or 160/25.

身长和头部长的比是160比25，记作160:25 或160/25。

":" is the sign, pronounced "bi". The number before the BI sign is called the preceding term, and the number after the BI sign is called the following term.

“：”是比号，读作“比”。比号前面的数叫作比的前项，比号后面的数叫作比的后项。

2. Zhao Fan walked 330 meters in 3 minutes. What's her walking speed?

2. 赵凡3分钟走了330米，她的行走速度是多少？

Three hundreds and thirty divided by three equals to one hundred and ten (m/min)

330÷3＝110(米/分)

Speed = distance ÷ time. The relationship between distance and time can be expressed by ratio: the ratio of Zhao Fan's distance to time is 330:3.

速度＝路程÷时间，路程和时间的关系可以用比来表示：赵凡走的路程和时间的比是330:3。

Dividing two numbers is also called the ratio of two numbers. The quotient of the first term divided by the second term of the ratio is called the ratio.

两个数相除又叫做两个数的比。比的前项除以后项所得的商叫作比值。

Ratio can be expressed as a fraction, as a decimal or as an integer.

比值可以用分数表示，也可以用小数或整数表示。

Think about it: 1. What is the relationship between ratio, fraction and division?

想一想： 1. 比、分数和除法之间有什么关系？

2. Can the term after the ratio be 0?

2. 比的后项可以是0吗？

3. Think about it. What are the properties of ratios?

3. 想一想，比有怎样的性质？

If the preceding term and the following term are multiplied or divided by the same number (except 0), the ratio remains the same. That's the fundamental property of PI.

比的前项和后项同时乘或除以相同的数(0除外)，比值不变。这是比的基本性质。

According to the basic properties of ratio, the ratio can be changed into the simplest integer ratio.

根据比的基本性质，可以把比化成最简单的整数比。

4. Can you make 14:21, 1/10:3/8 and 1.25:0.4 into the simplest integer ratio?

4. 你能把14:21、1/10：3/8和1.25:0.4化成最简单的整数比吗？

Lesson 2

Ming Ming: My weight is 30 kilos.

明明：我的体重是30千克。

Dad: My weight is 70 kilos.

爸爸：我的体重是70千克。

According to scientific research, the ratio of water in children's bodies to other substances is 4:1; The ratio of water to other substances in an adult's body is 7:3.

科学研究表面，儿童体内水分与其他物质的比是4:1；成年人体内水分与其他物质的比是7:3。

What questions can you ask?

你能提出什么问题？

Cooperative exploration

合作探索

1. How many kilograms of water and other substances do you have in your body?

1. 明明体内含的水分及其他物质各有多少千克？

Answer: Mingming has 24 kilograms of water in his body and 6 kilograms of other substances.

答：明明体内的水分有24千克，其他物质有6千克。

2. How many kilograms of water does dad have in his body?

3. 爸爸体内的水分有多少千克？

The beauty of "golden ratio"

“黄金比”之美

When an object is divided into two parts, it feels most beautiful when the ratio of the longer part to the whole is 0.618:1.This magic ratio is called the "gold ratio".For example, when a ballet dancer stands on tiptoe, the ratio of her lower body to her height is very close to the golden ratio, so she looks particularly beautiful.

把一个物体分成两部分,当较长的部分与整体的比是0.618:1时，给人的感觉是最美的。这个神奇的比被称为“黄金比”。例如,当芭蕾舞演员踮起脚来,下半身和身高的比非常接近黄金比，所以看起来特别的美。

People found in the nature of this strange ratio is almost everywhere, from animals and plants to human beings, from mathematics to astronomical phenomena, from daily life to artistic creation...

人们发现在自然界中这种奇的比几乎无所不在,从动植物到人类、从数学到天文现象、从日常生活到艺术创作……

Is there really such a comparison in life?

生活中真有这样的比吗?