比率-10點

A:B = B:C = 3:5
A:B = 3:5
B:C = 3:5

A:B = 3:5 = 3x3 : 5x3 = 9:15............(1)
B:C = 3:5 = 3x5 : 5x5 = 15:25............(2)

Subsitute (2) into (1),
A:B:C = 9:15:25

---------------------------------------------------------------
2a=5b=4c
i.e. 2a = 5b............(3)
and 2a = 4c............(4)

From (4):
2a = 4c
a = 2c
a:c = 2:1
a:c = 2x5 : 1x5 = 10:5............(5)

From (3):
2a = 5b
a:b = 5:2
a:b = 5x2 : 2x2 = 10:4............(6)

Subsitute (5) into (6),
a:b:c = 10:4:5

A:B=3:5.......其實即係等於9:15
B:C=3:5.......其實即係等於15:25

A:B:C
9 15
15 25

因此A:B:C=9:15:25

題目比左兩個B所以係要將佢變做同等份量,先可以寫出3者之間ge比例
A:B=3:5.......其實即係等於9:15
B:C=3:5.......其實即係等於15:25
因為而家兩個B同等份量,所以就可以將3個作出比較
A:B:C=9:15:25

2007-10-01 00:06:40 補充：
係呀....=.=睇漏左~~