1 进价为 210+700 =910 (元),所以销售总价为 910 + 340 = 1250 (元)
商品总件数为 1250 / 25 = 50 (件)
设从甲地采购X件,从乙地采购 50-X件,依题意
210/X - 700/(50-X) = 3.5
210*50 - 210X - 700X = 3.5(50X-X^2)
3000- 260X = 50X - X^2
X^2 - 310X +3000 = 0
(X-300)(X-10) =0
得 X1=300,X2=10
X1=300 不合题意,所以从甲地采购 10件,从乙地采购40件.
2.两月后售价为 625*(1-20%)(1+6%) = 530(元)
销售利润不变,则成本为 530 - (625-500) = 405(元)
设产品的成本价平均每月应降低 X,依题意,得
500(1-X)(1-X) = 405
即 100 -200X +100X^2 = 81
100X^2-200X +19=0
(10X-19)(10X-1)=0
得 X = 1.9 或 X=0.1
X = 1.9不合题意,取X=0.1=10%,故平均每月应降低10%