X,Y和差比率5:2

(X + Y) : (X - Y) = 5 : 2 (X + Y) / (X - Y) = 5 / 22(X + Y) = 5(X - Y)2X + 2Y = 5X - 5Y2Y + 5Y = 5X - 2X7Y = 3X7 / 3 = X / Y7 : 3 = X : Y該兩個數的比 = X : Y = 7 : 3


2011-02-13 23:11:35 補充：
方法二 :

設

x + y = 5k ....(1)

x - y = 2k .....(2)

(1) + (2) :

2x = 7k

(1) - (2) :

2y = 3k

所以 2x : 2y = 7k : 3k = 7: 3