第五单元

Unit five

The Animal World -- The Meaning and Nature of Decimals

动物世界——小数的意义和性质

Lesson One

第一课

The smallest bird in the world is the South American hummingbird. Its body length is only 0.05 meters, and its eggs weigh 0.46 grams

世界上最小的鸟是南美洲的蜂鸟，体长只有0.05米，它的蛋重0.46克。

With an egg weighing 0.365 kg and wings up to 3.6 meters long, the albatross is the longest-winged bird in the world.

信天翁的蛋重0.365千克，翅膀最长达3.6米，是世界上翅膀最长的鸟。

What questions can you ask?

你能提出什么问题？

Hummingbird body length 0.05 meters, 0.05 means what?

1.蜂鸟体长0.05米，0.05表示什么？

0.05 represents five hundredths, consisting of five hundredths.

0.05表示一百分之五，由5个一百分之一组成。

0.05 is made up of five 0.01's.

0.05有5个0.01组成。

An albatross's egg weighs 0.365 kg. What does 0.365 mean?

2.信天翁的蛋重0.365千克，0.365表示什么？

So 0.365 is three hundred sixty-five parts per thousand, which means one thousandth of 365 times

0.365就是一千分之三百六十五，表示365个一千分之一。

0.365 is made up of 365 0.001.

0.365由365个0.001组成。

Like 0.1, 0.05, 0.365... It's used this way to express the tenths, the hundredths, the thousandths... The number of is called a decimal.

像0.1，0.05 ，0.365…这样用来表示十分之几，百分之几，千分之几…的数，叫做小数。

Decimals are counted in tenths, hundredths, and thousandths, denoted as 0.1, 0.01, 0.001......

小数的计数单位是十分之一，百分之一，千分之一，记作0.1，0.01，0.001......

Decimals are made up of three parts

小数是由三部分组成的。

Integer part, decimal point, decimal part

整数部分、小数点、小数部分

Lesson Two

第二课

The grey squirrel weighs 0.504 kg and has a tail length of 1.98 decimeters

灰松鼠体重0.504千克，尾长1.98分米。

The rock squirrel weighs 0.300 kg and has a tail length of 1.45 decimeters.

岩松鼠体重0.300千克，尾长1.45分米。

It weighs 2.45 kg and has a tail length of 0.5 decimeter.

雪兔体重2.45千克，尾长0.5分米。

The hainan rabbit weighs 1.6 kg and has a tail length of 0.50 decimeters

海南兔体重1.6千克，尾长0.50分米。

What questions can you ask?

你能提出什么问题？

1. Which is longer, the grey squirrel's tail or the rock squirrel's?

1. 灰松鼠的尾巴与岩松鼠的相比，哪个长？

One point ninety-eight is one point forty-five

1.98＞1.45

The whole numbers are the same, and then compare the tenths

整数部分相同，再比较十分位。

9 > 4, so 1.98 > 1.45, grey squirrel's tail is long

9＞4，所以1.98＞1.45，灰松鼠的尾巴长。

2. Which is heavier than the snow rabbit or the hainan rabbit?

2. 雪兔的体重与海南兔的相比，哪个重？

Two point 45 is greater than one point six

2.45＞1.6

The integer part of 2.45 is 2 and the integer part of 1.6 is 1, 2 > 1, so the snow rabbit is heavy.

2.45的整数部分是2，1.6的整数部分是1，2＞1，所以雪兔重。

So let's think about how do we compare decimals?

想一想怎样比较小数的大小呢？

Snow rabbit's tail compared with hainan rabbit, which long?

3. 雪兔的尾巴与海南兔的相比，哪个长？

0.5=0.50

what do you find

你发现了什么？

What do you find by comparing?

通过比较你有什么发现？

The size of the decimal remains the same by adding or removing a zero to the end of the decimal.

小数的末尾添上0或去掉零小数的大小不变。

That's a property of decimals.

这是小数的性质。

Could the weight of the rock squirrel and the grey squirrel be written more simply?

4.岩松鼠和灰松鼠的体重可以写得更简便些吗？

Can you write 0.9, 6.07 and 5 into three decimal places without changing the size of the numbers?

不改变数的大小，你能将0.9，6.07和5改写成三位小数吗？

Lesson Three

第三课

One kiwi egg weighs about the same as 10 brocade eggs or 100 cuckoo eggs or 1,000 hummingbird eggs.

1个几维鸟蛋的质量大约相当于10个锦鸡蛋或100个杜鹃蛋或1000个蜂鸟蛋的质量。

What questions can you ask?

你能提出什么问题？

How much does a brocade egg, a cuckoo egg and a hummingbird egg weigh?

1.锦鸡蛋、杜鹃蛋，蜂鸟蛋各有多重呢？

So let's get our calculator out to figure that out.

我们用计算器来算一算。

Four hundred sixty five divided by one hundred equals four sixty five

460.5÷10=46.05

Four hundred sixty five divided by one hundred equals four sixty five

460.5÷100=4.605

Four hundred sixty five divided by one thousand equals zero four sixty five

460.5÷1000=0.4605

If you look at the formula above, what do you find?

观察上面的算式，你发现了什么？

I saw a decimal shrink to a tenth, a hundredth, a thousandth, and the decimal point move one, two, and three places to the left.

我发现一个小数缩小到它的1/10，1/100，1/1000，小数点分别向左移动一位、两位、三位。

If you expand 0.08 to 10 times, 100 times, or 1,000 times, what is the result?

把0.08分别扩大到它的10倍、100倍、1000倍，结果是多少？

Zero point eight times ten is eight

0.08×10=0.8

Zero point eight times one hundred equals eight

0.08×100=8

Zero point eight times one thousand is eighty

0.08×1000=80

Extending 0.08 to 10, 100, or 1,000 times that is to take the decimal point...

把0.08分别扩大到它的10倍、100倍、1000倍就是把小数点…

If you reduce 40.59 to one tenth, one hundredth, one thousandth of 40.59, what do you get？

把40.59分别缩小到它的1/10，1/100，1/1000，结果是多少？

If I multiply it by 10 times, 100 times, 1,000 times, what do I get?

分别扩大到它的10倍100倍1000倍，结果是多少？

Lesson Four

第四课

I weighed 200 grams at birth

我出生时体重是200克

I weigh 10.5 kilos now

我现在的体重是10.5千克。

What questions can you ask?

你能提出什么问题？

1. How much more do swans weigh when they grow up than at birth?

1.天鹅长大后比出生时体重增加了多少？

What if the units are different?

单位不相同怎么办？

Let's rewrite it in the same units.

先改写成相同的单位。

So let's rewrite kilograms as grams.

把千克改写成克。

1 kilogram is equal to 1000 grams.

1千克=1000克。

10.05 times 1000, you can just move the decimal point three to the right.

10.05×1000，可以直接把小数点向右移动三位。

Ten point five times one thousand is ten point five hundred grams

Ten thousand five hundred minus two hundred equals ten thousand three hundred grams

10500-200=10300（克）

Let me rewrite grams as kilograms.

把克改写成千克。

1 kilogram is equal to 1000 grams.

1千克=1000克。

200÷1000 you can just move the decimal point three to the left.

200÷1000可以直接把小数点向左移动三位。

Two hundred grams are equal to 0.2 kilograms

200克=0.2千克。

Half past ten minus two equals 10.3 kilograms

10.5-0.2=10.3（千克）

Can you solve the following problems?

你能解决下面的问题吗？

One meter twenty-six centimeters is equal to -- meters?

1米26厘米等于——米？

2.39 kilograms equals -- kilograms -- grams?

2.39千克等于——千克——克？

Lesson Five

第五课

The length of the egg is about 13.9 cm.

绿毛龟蛋的长径约13.9厘米。

The length is about 4 centimeters

长径约是4厘米。

How many centimeters is the wide diameter of the green hairy turtle egg?

绿毛龟蛋的宽径大约是多少厘米？

What other questions can you ask?

你还能提出什么问题？

1. Why are the results different between Xiao Hua and Xiao Ming?

1.小华和小明说的结果为什么不一样呢？

They're talking about approximations.

他们说的是近似数。

How do you approximate a decimal?

怎样求小数的近似数呢？

To approximate decimals, we can use the "round off" method as well as integers

求小数的近似数和整数一样，也可以用“四舍五入法”。

How many centimeters is the wide diameter of the green hairy turtle egg? (Keep a decimal place.)

2.绿毛龟蛋的宽径约是多少厘米？（保留一位小数。）

Two point four centimeters is about two point four centimeters

2.04厘米≈2.0厘米。

When approximating numbers, keep integers, indicating that they are accurate to the ones place;

求近似数时，保留整数，表示精确到个位；

To keep one decimal, it's accurate to the tenth place

保留一位小数，是精确到十分位；

Keep two decimal places to indicate accuracy to the hundredth......

保留两位小数，表示精确到百分位......

Can you rewrite the numbers on the bottom line as numbers in tens or billions?

你能把下面横线上的数改写成用”万”或“亿”作单位的数吗？

The highest flying bird is a swan, which can reach a maximum of 17,000 meters.

飞得最高的鸟是天鹅，最高能达17,000米。

Ornithologists estimate that there are 9,680,000,000 birds in the world today.

鸟类学家估计，目前世界上鸟类总数约为99680000000只。

There is one thousand and 7,000 ones in 17,000, and the integer part should be 1.

17,000里有一个万和7000个一，用”万”作单位，整数部分应该是1。

Point the decimal point to the right of the ten thousand place and add the word "ten thousand" after the number.

在万位的右边点上小数点，在数的后面加上“万”字。

Seventeen thousand is one hundred seventy thousand

17,000=1.7万

There are 996 billion and 80 million in 99680000000. The integer part should be 996.

99680000000里有996个亿和8000个万，用“亿”做单位，整数部分应该是996。

99.68 billion is equal to 99.68 billion

99680000000=996.8 亿

To change a number to a number in tens or hundreds of millions, do this by...

把一个数改成用“万”或“亿”作单位的数，方法是…

Can you approximate it by taking the reserved integer 99.68 billion?

你能把996.8亿保留整数求它的近似数吗？