Question

一个长方形,周长是280cm,长和宽的比是5:2，它的面积是多少？

用比例方法 还有过程

Answer 1

长:宽=5:2
2长=5宽 (注：根据内项之积等于外项之积得到)
长=5/2宽
2（长+宽）=280
2（5/2宽+宽）=280
宽=40cm
长=5/2宽=100
面积=4000平方厘米

追问

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追答

诚心答题，过程慢了点，请不必发这些

Answer 2

解：设长方形的宽为x cm, 5/2 x cm.
2x(5/2x)+2x=280
5x+2x=280
7x=280
x=40
5/2x=100cm
S（面积）=100x40=4000cm^2

Answer 3

280/2=140
140*5/7=100
140*2/7=40
100*40=4000

追问

.

Answer 4

设边长为x
2(5x+2x）=280
2*7x=280
14x=280
x=20
s=a*b
=（5*20）*（2*20）
=100*40
=4000（cm2）

追问

3Q 3Q

Answer 5

4000