Area and volume

a)Total area of the oceans on the Earth
=4π(6400)²*70%km²
=0.7*4π(40,960,000)²km²
=114,688,000πkm²
=360,302,978km²(cor. to nearest integer)

bi)Total area of the oceans on the globe
=(1000*100)*114,688,000π/40,000,000cm²
=900757cm²(cor. to nearest integer)

bii)Actual area of China
=60*40,000,000/(100*1000)km²
=24,000km²

2008-06-22 17:11:10 補充：
球體表面積積:4πr²
1m=100cm
1km=1,000m=100,000cm
1m²=10,000cm²
1km²=1,000,000m²=10,000,000,000cm²
1m³=1,000,000cm³
1km³=1,000,000,000m³=1,000,000,000,000,000cm³

2008-06-22 17:13:51 補充：
biTotal area of the oceans on the globe
=114,688,000πkm²÷4,000,000²cm²
=10,000,000,000*114,688,000π÷40,000,000²cm²
=2252cm²
biiActual area of China
=60*40,000,000²cm²÷1km²
=60*40,000,000²÷10,000,000,000km²
=9,600,000km²

PS我分別用²同³代替^2同^3，希望您容易d睇。

Find the total area of the oceans on the Earth.
*Assume that the Earth is a sphere

the total area of the sphere is 4丌r^2
the tolal area of the Earth is :
4丌(6400)^2


It is known that nearly 70% of the surface of the Earth are oceans
the total area of the oceans on the Earth is :
4丌(6400)^2 * 70%
= 360302978 km^2 (nearest km^2)

b)


1m = 100cm
1km =1000m = 1000*100 cm =100000cm
1km^2 = 100000^2 cm^2 = 1 x 10^10 cm^2

1:40 000 000 We can know 1cm to 40 000 000 cm
= 1 cm to 400 * 1000 * 100 cm
= 1 cm to 400km
Therfore 1cm^2 to 400^2 km^2

The total area of the ocean in the Earth is 360302978 km^2

Therfore the total are of the oceans (in cm^2) on the globe is
360302978 / 400^2
= 360302978 / 160000
= 2252 cm^2 (4.s.f)

b)ii

1cm^2 to 160000 km^2

If the area of China on the globe is 60 cm^2, find the actual area (in km^2) of China.

The area of China in the Earth is :
60 * 160000
=9600000 km^2

可以的話 請簡述cm m km cm^2 m^2 km^2 cm^3 m^3 km^3各個單位的轉換方法.

1m = 100cm
1km = 1000m = 100 000 cm

1m^2 = 100^2 cm^2 =10 000 cm^2
1km^2 = 1000^2 m^2 = 1000 000 m^2
1km^2 = 100 000 ^2 cm^2 = 10 000 000 000 cm^2 (1 x 10^10 cm^2)

1m^3 = 100^3 cm^3 =1000 000 cm^3
1km^3 = 1000^3 m^3 = 1 000 000 000 m^3
1km^3 = 100 000^3 cm^3 = 1 000 000 000 000 000 cm^3 (1 x 10^15 cm^3)

2008-06-22 16:44:02 補充：
回002:

form 3 兩條公式你要記住

L = length
A = area
V = volume

對於simular object 也好,ratio也好
L:A:V = 1次:2次:3次
即是

A1:A2 = L1 ^2 : L2 ^2
V1:V2 = L1 ^3 : L2^3

要是長度 1cm to 400km 面積則 1cm^2 to 400^2 km
要是長度 1cm to 400km 體積則 1cm^3 to 400^3 km