kobel51 wrote:On a companysponsored cruise, 2/3 of the passengers were company employees and the remaining passengers were their guests. If 3/4 of the companyemployee passengers were managers, what was the number of companyemployee passengers who were NOT managers?
1) There were 690 passengers on the cruise
2) There were 230 passengers who were guests of the company employees.
One approach is to use the Double Matrix Method. This technique can be used for most questions featuring a population in which each member has two characteristics associated with it.
Here, we have a population of passengers, and the two characteristics are:
 company employee or not company employee
 a manager or not a manager
Aside: To learn more about this technique, watch our free video: http://www.gmatprepnow.com/module/gmatwordproblems?id=919
Okay, onto the question...
Target question: What was the number of companyemployee passengers who were NOT managers?
Given: 2/3 of the passengers were company employees and the remaining passengers were guests. 3/4 of the companyemployee passengers were managers.
Let's begin by setting up our diagram to show the two sets of characteristics:
Since we don't know the total number of passengers, let's let x = total number of passengers:
If "
2/3 of the passengers were company employees and the remaining passengers were guests," then 1/3 are guests. This means the sum of the boxes in the lefthand column is (2/3)x and the sum of the boxes in the righthand column is (1/3)x:
Then we're told that "
3/4 of the companyemployee passengers were managers"
So 3/4 of the (2/3)x passenger were managers.
3/4 of (2/3)x = (1/2)x, so (1/2)x passengers were managers:
Since the sum of the two boxes in the leftcolumn must add to (2/3)x, we can conclude that the other box must be (1/6)x, so we can add that here.
IMPORTANT: Since none of the guests were managers, we know that the topright box contains zero passengers as follows:
Finally, the sum of the two boxes in the rightcolumn must add to (1/3)x, we can conclude that the other box must be (1/3)x, so we can add that here.
Okay, our goal is to determine
the number of companyemployee passengers who were NOT managers. In other words, we want to know the number of passengers in the bottomleft box. So, let's place a STAR in this box to remind us of this:
We're now ready to check the statements...
Statement 1: There were 690 passengers on the cruise
In other words, x = 690
From this, we can take our diagram and plug in 690 for x:
As we can see, we can determine the number of passengers in every box, which means we can
definitely determine
the number of companyemployee passengers who were NOT managers
Since we can answer the
target question with certainty, statement 1 is SUFFICIENT
Statement 2: There were 230 passengers who were guests of the company employees.
In other words, the boxes in the lefthand column have a sum of 230
If (1/3)x = 230, we can determine the value of x.
Once we know the value of x, we can we can
definitely determine
the number of companyemployee passengers who were NOT managers
Since we can answer the
target question with certainty, statement 2 is SUFFICIENT
Answer =
D

Once you are familiar with the Double Matrix Method, you can attempt these additional practice questions:
Easy Problem Solving questions

http://www.beatthegmat.com/theaamaadmipartyt272242.html

http://www.beatthegmat.com/financemajorsnonfinancemajorsoverlappingsetquestiont167425.html
Medium Problem Solving questions

http://www.beatthegmat.com/probabilityquestiont273360.html

http://www.beatthegmat.com/postedspeedlimitt272374.html

http://www.beatthegmat.com/motelt271938.html

http://www.beatthegmat.com/oftheapplicantspassesacertaintest15t270255.html

http://www.beatthegmat.com/openingnightandlatepatronst264869.html

http://www.beatthegmat.com/dsfrenchjapaneset222297.html
Difficult Problem Solving questions

http://www.beatthegmat.com/ratioproblemt268339.html

http://www.beatthegmat.com/overlappingsetsquestiont265223.html

http://www.beatthegmat.com/fractionst264254.html

http://www.beatthegmat.com/overlappingsetst264092.html

http://www.beatthegmat.com/mba/2011/05/09/randomdoublematrixquestion2
Easy Data Sufficiency questions

http://www.beatthegmat.com/forwhatpercentofthosetestedforacertaint270596.html

http://www.beatthegmat.com/dsquestt187706.html
Medium Data Sufficiency questions

http://www.beatthegmat.com/setsmatrixdst271914.html

http://www.beatthegmat.com/eachofpeoplevotedonceinanelectionxt271375.html

http://www.beatthegmat.com/amanufacturert270331.html

http://www.beatthegmat.com/incostumeforhalloweent269355.html

http://www.beatthegmat.com/mba/2011/05/05/randomdoublematrixquestion1
Difficult Data Sufficiency questions

http://www.beatthegmat.com/doublesetmatrixquestiont271423.html

http://www.beatthegmat.com/setst269449.html

http://www.beatthegmat.com/mba/2011/05/16/randomdoublematrixquestion3
Cheers,
Brent