Well organized....

But for weighted average, I feel an alternative approach will be easy

**Quote:**

Percents and weighted averages

Cereal K is 10% sugar and Cereal B is 2% sugar. What should be the ratio of them to produce a 4% sugar cereal?

Technique: Pick a smart number for one of the quantities and call the other quantity x. For example, picking 100 grams for Cereal K:

100*0.1 + 0.02*x = 0.04(100 + x) 10 + 0.02x = 4 + 0.04x

0.02x = 6 x = 300

So, the ratio is 3 parts of Cereal B to each part of Cereal K, or 1:3

10k+2b=4(k+b) ==>6k=2b ==> k:b = 1:3**Quote:**

Percent Change and Weighted Averages

The revenue from pen sales was up 5%, but the revenue from pencil sales declined 13%. If the overall revenue was down 1%, what was the ratio of pen and pencil revenues?

105 + 0.87x = 0.99(100 + x) 6 = 0.12x x = 50

So, the ratio is 2:1

105Pen+87Pencil=99(Pen+Pencil) ==> 6Pen = 12Pencil ==> Pen : Pencil = 2:1Let me know your thoughts...

In fact this approach can be applied to any mixture problem : add/replace/remove combinations

_________________

Labor cost for typing this post >= Labor cost for pushing the Kudos Button

http://gmatclub.com/forum/kudos-what-are-they-and-why-we-have-them-94812.html