Data Sufficiency

Hi ppl,

I had a slight doubt in the underlying concept of this question. Obtaining the answer per say is pretty straightforward, but I seem to find a discrepancy in my understading of the concept(under the theoretical situation where this was in fact a PS, I believe i would have been in a soup (Interested few can take my last statement as an SC)) . Would like to clarify my conceptual understanding.

The question is #75 from the Official Guide OG11 DS practice set.

In a certain office, 50% of the employees are college graduates and 60% of the employees are over 40 years old. If 30% of those over 40 have master's degrees, how many of the employees over 40 have Master's degrees?

1) Exactly 100 of the employees are college graduates.
2) Of the employees 40 years old or less, 25 percent have master's degree.


Clearly the answer would be A, as only 1) provides us with an actual number to work with rather than percentage, and with the given percentage info, this is workable.

Here's what I don't understand, isn't the information given in 2) already known to us? I mean they initially say 50% of the total are Graduates (implying whether above or below 40, 50% of them are graduates). It is also given that 30% of those over 40 have a master's degree - allowing me to believe that the left over folk who are graduates are less than 40.

Therefore,
total graduate percentage - >40 graduate percentage = <40 graduate percentage

Thus,
50%(of total ppl)-30%(of total ppl) = 20%(of total ppl) .

But now 2) tells me that this figure is 25%. What have I understood wrong? I usually notice a pattern from DS OG,where even though the amount of information given by 1), 2) or 1) and 2) together is mis-leading, it is never contradictory. Am i right in assuming this?

Any help would be greatly appreciated.

thanks and keep cracking.

In a certain office, 50% of the employees are college graduates and 60% of the employees are over 40 years old. If 30% of those over 40 have master's degrees, how many of the employees over 40 have Master's degrees?

1) Exactly 100 of the employees are college graduates.
2) Of the employees 40 years old or less, 25 percent have master's degree.


U have 2 parameters - Age (>40, <40) and master's degree (have. do not have) so you have 4 groups.
We are given that 30% of those over 40 have master's degrees.
To answer the question you should know
the total number of people or any of 4 groups


(1)
the total number of people or any of 4 groups is given
SUFF

(2)
You are given the percentile of <40 with MD
You can find percentile of other groups
But what is the total number of people?
INSUFF

Thus, A

4meonly, at the outset wow thank you for the detailed image as well. I REALLY appreciate your effort in helping for this one.But there are couple of things, I disagree or do not seem to understand with your reply. My humble requests for clarification Your table is perfect for visualizing and it's immediately what I did as well.(Assuming T to be the total number of people)Just a couple of things:

• My table looks similar to yours except instead of the question mark I have 18% already from the main question. Let me elucidate.

• The question tells us that 60% of the total number of employees are >40. So total number of employees >40 = 0.6T. The main part of the question itself also tells us that "30% of those over 40 have master's degrees" which would mean 30% of 60% of T are the total number of employees that are graduates and over 40. i.e 0.18T

• Therefore T alone is enough to solve our problems. Stem 1 gives us this. Therefore A is SUFFICIENT.

• Now here's the tricky part. Stem 2 tells us "Of the employees 40 years old or less, 25 percent have master's degree". This as you point out correctly translates to 10% or 0.1T. Stem 2 alone is INSUFFICIENT

• The Answer therefore should be A (OG 11 confirms this as well)

• I actually didn't have a problem in the answer for this question per say. What I do have a problem is that I could have found out the information given in Stem 2 Even before they gave it. I have the figure 18% already (as explained above- which you do not have though- which is why I want to know if there was something I did wrong). Having the figure 18% automatically tells us from the table that the number of employees <40 and who are graduates is in fact 50%T-18%T=32%T or in other words 0.32T.

• Here in lies the confusion. OG 11 never contradicts itself in DS (from what I have noticed) They leave out info or give more than what is required. But seldom do they contradict. This is a case where I find a contradiction. "That" is my problem. Not the solution for this sum per say which I believe to be "A"

• Did I do something wrong in assuming? or can I safely assume that OG and thus the GMAC can at times contradict itself?

Thanks for the efforts.

k2gopal,
sorry, my fault - I overlooked that "If 30% of those over 40 have master's degrees" is already given.
I was not attentive with this question - I made corrections in my post.


For sure, answer is A


About contradiction - for me it is possible.
I saw such situations. The main question is not to find the answer to the Q but to state whether data is suff or not.
Here 1 stem gives the opportunity to answer the question, 2nd stem is not suff.
My personal opinion: 1 stem and 2nd stem usually do not contradict each other, but they can do so.
Hope I helped you.

Thanks 4meonly. That' s exactly what I wanted to know . Anyone else have an opinion on the contradiction between stems in DS?

Cheers
K