Venn Diagram vs. Table Matrix?

[Barbarosa]

I am trying to figure out when is one method better than the other. Sometimes, the wording of the problems tricks me into using the wrong method of the two and I lose time. So how can I tell when exactly I should use Venn diagram and when I should use matrix?

Thanks

[jnelson0612]

I am trying to figure out when is one method better than the other. Sometimes, the wording of the problems tricks me into using the wrong method of the two and I lose time. So how can I tell when exactly I should use Venn diagram and when I should use matrix?

Thanks

Gladly!

Any time that you have a population described two different ways use the matrix. For example, some members of a country club play golf, some play tennis, some play both, and some play neither. Thus, every member either 1) plays golf or does not play golf and 2) plays tennis or does not play tennis.

If you have three possible ways to describe the population use three overlapping circles and create a Venn diagram. For example, in a school some students take French, some take German, and some take Spanish. In this case, some students may take only one language, some may take two, and some may take all three.

One final note: the questions using three dimensions can be incredibly difficult and time consuming. Unless you are shooting for an 80th percentile quant or better you may want to skip them.

[Barbarosa]

Hello there,

Well I am actually now around the 80th percentile. I took the official GMATPrep couple times and I scored 45 and 44 in quant section. When I started to prepare I was completely off from a good score. By the way, I honestly think that MGMAT guides are absolutely the best on the market!

Now, I should have been more specific with my question. I know how to use the Venn diagram when I have to draw three circles. The one I mean was the two-circles Venn diagram. For example, when you have a-x, x, b-x inside the two circles and possibly c outside of the circles. That is when I made mistakes.

I still cannot figure out whether these two approaches would always provide me with a solution in the same problem. Or, there is a difference between the two. So my question is, if a person can solve a problem with matrix, does that automatically mean that he or she should be able to solve the problem with Venn also?

You input would be much appreciated.

[jlucero]

I'm not sure there's one exact way to answer this question, but here's my theory. Venn diagrams are great b/c of their simplicity, while the Matrix is great b/c it exhausts all nine pieces of information that you can possibly get from a Venn diagram.



In this diagram there are numbers representing three specific items- only A (3), only B (1), and both A&B (2). If a question is specifically giving you these elements (or a simple combination of them, i.e. all of A (1&2)), then go with the Venn Diagram.

But if the question gets more convoluted and includes a neither category (let's call this 4), or says 20% of not-set A (20% x (1&4)), that's where the advantage of using the Matrix, which includes 9 different combinations of groups 1234, comes in.

Long story short, there are two strategies- 1) try out the Venn diagram when there is no "neither" category, but as soon as you get stuck, move to the Matrix or 2) always use the matrix, but be careful if there is no "neither" or "both" category.

[Barbarosa]

I thought most of the time that Venn and matrix are for completely problems and I recently found out that sometimes you can do problems with both of these approaches.

Thanks for your input.

[tim]

:)