Rates and Ratios

Because the 3 triangles are equilateral, they are similar.

By similar triangles, the area of the smaller one : the area of the larger one = (2/4)^2

the area of the smaller one / the area of the larger one = 1/4
the area of the smaller one = 80 *1/4 = 20 cm^2
the area of the middle one/ the area of the larger one = (3/4)^2
the area of the middle one = 80 *9/16 = 45 cm^2

面積比例=邊長二次方比例
所以三個三角形的面積比例是4:9:16
4/16=x/80
x=20cm^2

9/16=x/80
x=45cm^2

所以其他兩個三角形的面積分別是20cm^2,45cm^2

如果系等邊三角形
最大ge面積系80cm^2=比理四

將距除翻變一份
80/4=20

再成翻另外兩個比例
第一個三角面積:
20x2=40cm^2
第二個三角面積:
20x3=60cm^2

總之將一份量找出來...就可完成任何面積
例如算所有面積等於
(2+3+4)x20=180cm^2