MGMAT CR 4th Ed

I initially put C as the answer... but I realize that I might have misinterpreted the answer stem. When the answer states that Judd has a greater percentage of alumni in the Air Force, I thought this meant that of ALL the people in the air force, Judd had a greater percentage of alumni.

Nevertheless, D makes sense. To see why, suppose that there were no graduates of Knoxworth who were serving in the military and not in the Air Force... in other words, all graduates who were in the military were also in the Air Force. This means that everybody in the school is in the Air Force. But, this is a contradiction! Knoxworth has the most graduates as a whole, according to the passage, but Judd has the largest number serving in the Air Force.

This is a little tricky one. Initially, I chose C but if you look closely, D makes sense as we dont have any information about Knoxworth HS's alumni. It just talks about the graduates of this school. Now the stimulus states that "most of the knoxworth's graduates serve in the military as a whole including army, airforce, navy, marines and coast guards". This means there are some who are not serving in the airforce but are in the other branches. Hence choice D.

Hope that helps... Please let me know if my expalanation does not make sense.

This is a tricky question that employs some common GMAT traps! This is an inference question, so we're looking for the answer that must be true based on the information in the prompt.

Answer choice C seems to be tempting to a few of you -- but remember, percentages are NOT the same as numbers! Say Judd Academy has a total of 100 alumni, and 10 of these serve in the Air Force. Now, say Knoxville has 50 alumni, and 7 of these serve in the Air Force, 5 in the Army, 3 in the Navy. All of the conditions of the prompt are satisfied: Judd has the largest number of alumni serving in the Air Force, and Knoxville has the most alumni serving in the military. However, Knoxville has a greater PERCENTAGE of alumni serving in the Air Force -- 14% for Knoxville versus 10% for Judd. The GMAT will often try to confuse you with numbers versus percents, so keep your eyes open for this common wrong answer choice.

Now let's look at answer choice D. Again, say that Judd Academy has 10 alumni serving in the Air Force. In order for Knoxville to have the highest number of alumni serving in the military, the school must have at least 11 alumni in the military. However, if 10 or more of these Knoxville alumni serve in the Air Force, then the condition laid out in the prompt that Judd has the greatest number of alumni in the Air Force will not be satisfied. Therefore, some of the Knoxville alumni must be serving in a branch of the military other than the Air Force.

I often find that with number/percent CR questions like this, it can be helpful to approach them almost like a Quant problem -- create potential scenarios by plugging in numbers, testing cases, and trying to prove the statement false!

@Jen,

So by meaning "some graduates of Knoxworth High school are serving in the military but not in the Air force" - we mean All of them who is serving Military is not serving Air force but some of them might be serving Air force...... did I get this right.

But initially what I understood is, some of them are serving Military and no one is serving Air force.....

Thanks.

* Edited the post after Jen's reply to make it clear.

@gtvisa2002

Great question! It is critical to interpret choice D correctly in order to answer this question. A restatement of answer choice D could be: Not all of the Knoxworth alumni who are serving in the military are serving in the Air Force. That is, there are some Knoxworth alumni who are in the military, but who are serving in a unit other than the Air Force.

If I'm understanding you correctly, your initial reading was: Some Knoxworth graduates are serving in the military, but no Knoxworth graduates are serving in the Air Force. This is not actually what answer choice D is saying, and this distinction significantly impacts your reading of the question and your ability to get to the right answer.

Hope this helps!

You are right Jen. Thats what I read from the statement earlier.
Now I understand the meaning.

Thanks for your help.

Thanks to everybody.

Option D is very tricky because the kind of language what they have used.