#74 DS question from OG

k2gopal · Posted: Wed Oct 15, 2008 2:39 pm Post subject: #74 DS question from OG

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. Wink

4meonly · Posted: Thu Oct 16, 2008 6:10 am Post subject:

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

k2gopal

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 Smile

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.

30% of those over 40 have master's degrees

0.18T

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

"Of the employees 40 years old or less, 25 percent have master's degree"

OG 11 confirms this

(as explained above- which you do not have though- which is why I want to know if there was something I did wrong)

"That"

"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.

4meonly · Posted: Thu Oct 16, 2008 10:40 pm Post subject:

k2gopal,
sorry, my fault - I overlooked that "If 30% of those over 40 have master's degrees" is already given. Sad

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.

k2gopal · Posted: Fri Oct 17, 2008 1:12 pm Post subject:

Thanks 4meonly. That' s exactly what I wanted to know Smile

. Anyone else have an opinion on the contradiction between stems in DS?

Cheers
K