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explanation on the image (link attached)

the orange and blue are no accident. go gators!

click here to see the solution

[editor: this link is broken - for an updated link, see below.]

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Ron is a Director of Curriculum Development at Manhattan GMAT. He has been teaching various standardized tests for almost 20 years.

He wears white after Labor Day, gets 55% of his calories from protein, and takes standardized tests for fun.

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no problem - i'm glad you found it useful. that is a cool problem.

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Ron is a Director of Curriculum Development at Manhattan GMAT. He has been teaching various standardized tests for almost 20 years.

He wears white after Labor Day, gets 55% of his calories from protein, and takes standardized tests for fun.

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haha, i just realized i posted the wrong answer on the solution sheet.

the reasoning is all correct, but the answer is supposed to be 'a'

just testing you guys.
really.

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Ron is a Director of Curriculum Development at Manhattan GMAT. He has been teaching various standardized tests for almost 20 years.

He wears white after Labor Day, gets 55% of his calories from protein, and takes standardized tests for fun.

Pueden hacerle preguntas a Ron o en inglés o en español.

If you send Ron a private message, please allow 1-2 weeks for a response.

Learn more about ron

here's an updated link

http://www.postimage.org/image.php?v=gx1ffBD9

the answer still mistakenly says 'B' on the bottom of the page. (it's supposed to be (a))

_________________
Ron is a Director of Curriculum Development at Manhattan GMAT. He has been teaching various standardized tests for almost 20 years.

He wears white after Labor Day, gets 55% of his calories from protein, and takes standardized tests for fun.

Pueden hacerle preguntas a Ron o en inglés o en español.

If you send Ron a private message, please allow 1-2 weeks for a response.

Learn more about ron

well -- no matter what approach you take, you should always make separate matrices for statements (1) and (2) -- even if the row and column headings are the same (which they usually will be).
the reason is simple: statement (1) contains information that's not in statement (2), and statement (2) also contains information that's not in statement (1). if you try to do all of this in one matrix, the potential for confusion is way too high, especially because you have to write on plastic with a marker (no pencils or erasers!).

if you want to make the full-on Favorable/Unfavorable/Not Sure matrix for statement (1), you can do so.
if you do this, instead of a simple "40" in the "not favorable" row (which encompasses both "unfavorable" and "not sure"), you'll have an "x" and a "40 - x", respectively, in separate rows for "unfavorable" and "not sure" (or vice versa). overall, the problem will still work out the same way, though -- if you do the algebra through the rest of the table, you'll notice that all of the x's cancel out of the square that you want.
still, though, it's good to be able to recognize that you don't have to consider any distinctions other than "favorable"/"not favorable" in that problem, though -- this sort of recognition is the linchpin of several other problems with multiple distinctions between items, too. for example, see problem #107 in the OG12 data sufficiency section.

_________________
Ron is a Director of Curriculum Development at Manhattan GMAT. He has been teaching various standardized tests for almost 20 years.

He wears white after Labor Day, gets 55% of his calories from protein, and takes standardized tests for fun.

Pueden hacerle preguntas a Ron o en inglés o en español.

If you send Ron a private message, please allow 1-2 weeks for a response.

Learn more about ron

I wouldn't do much math for this problem. We're looking for the number who voted favorable for both M and N. In other words, the overlap between the 2 favorable groups.

The big idea with overlapping group problems is to subtract the overlap. When we count the number who voted favorable for M and the number who voted favorable for N, the number who voted favorable for both -- the overlap -- gets counted twice. So that we don't double-count the overlap, it must be subtracted from the total:

Total favorable = Favorable for M + Favorable for N - Favorable for Both

Since we know that 40 voted favorable for M and that 30 voted favorable for N, to solve for the number who voted favorable for both -- the overlap -- we need to know the total number of favorable votes.

Statement 1:
If 40 did not respond favorable for either candidate, then the total who did respond favorable was 100-40 = 60.
60 = 40 + 30 - both.
Both = 10.
Sufficient.

Statement 2:
Tells us the overlap between the 2 unfavorable groups. Doesn't help us to determine the overlap between the 2 favorable groups.
Insufficient.

The correct answer is A.

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Mitch Hunt
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