甲、乙两包糖的质量比是4:1,从甲包取出130克放入乙包后,甲、乙两包糖的质量比为7:5.原来甲包有多少克糖?
解:4÷(4+1)=
![](http://thumb.1010pic.com/pic5/latex/602.png)
,
7÷(7+5)=
![](http://thumb.1010pic.com/pic5/latex/450.png)
,
130÷(
![](http://thumb.1010pic.com/pic5/latex/276818.png)
)×
![](http://thumb.1010pic.com/pic5/latex/602.png)
,
=130÷
![](http://thumb.1010pic.com/pic5/latex/3661.png)
×
![](http://thumb.1010pic.com/pic5/latex/602.png)
,
=600×
![](http://thumb.1010pic.com/pic5/latex/602.png)
,
=480(克);
答:原来甲包有480克糖.
分析:根据甲、乙两包糖的质量比是4:1,甲包糖的质量占总质量的
![](http://thumb.1010pic.com/pic5/latex/171098.png)
=
![](http://thumb.1010pic.com/pic5/latex/602.png)
,从甲包取出130克放入乙包后,甲包糖的质量占总质量的
![](http://thumb.1010pic.com/pic5/latex/276819.png)
=
![](http://thumb.1010pic.com/pic5/latex/450.png)
,取出的130克所对应的分率是(
![](http://thumb.1010pic.com/pic5/latex/276818.png)
),用分数除法求出甲、乙两包糖共有多少,进而解答即可.
点评:解答此题,甲、乙两包糖的总质量不变,求出取出130克糖所对应的分率是解题的关键.