AbeNeedsAnswers wrote: ↑Fri Jun 05, 2020 6:26 pm
OG2021PS137.png
In a poll, 200 subscribers to Financial Magazine X indicated which of five specific companies they own stock in. The results are shown in the table above. If 15 of the 200 own stock in both IBM and AT&T, how many of those polled own stock in neither company?
A. 63
B. 93
C. 107
D. 122
E. 137
E
Another approach is to use the
Double Matrix Method. This technique can be used for questions featuring a population in which each member has two characteristics associated with it (aka overlapping sets questions).
Here, we have a population of 200 magazine subscribers and the two characteristics we need to focus on are:
 owns stock in IBM or does not own stocks in IBM
 owns stock in AT&T or does not own stocks in AT&T
So we can set up our diagram as follows:
If 30 of the 200 subscribers own stock in AT&T, then the other 170 subscribers do NOT own stock in AT&T
If 48 of the 200 subscribers own stock in IBM, then the other 152 subscribers do NOT own stock in IBM
When we add this to our diagram we get the following:
At this point, we can complete the rest of our diagram:
Since the bottomright square represents subscribers who own stock in neither company, the correct answer is E
Aside: We can also use Venn diagrams and formulae to solve overlapping sets questions. However, as difficulty levels increase, it becomes harder to apply those other approaches, whereas the Double Matrix Method works every time.
This question type is
VERY COMMON on the GMAT, so be sure to master the technique.
To learn more about the Double Matrix Method, watch this video:
https://www.gmatprepnow.com/module/gmat ... ems?id=919
Once you’re familiar with this technique, you can attempt these additional practice questions:
Easy Problem Solving questions

https://www.beatthegmat.com/financemajo ... 67425.html
Medium Problem Solving questions

https://www.gmatprepnow.com/module/gmat ... /video/920

https://www.beatthegmat.com/postedspeed ... 72374.html

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

https://www.beatthegmat.com/oftheappli ... 70255.html

https://www.beatthegmat.com/openingnigh ... 64869.html

https://www.beatthegmat.com/atleast100 ... 74669.html

https://www.beatthegmat.com/prblemsolvingt279424.html
Difficult Problem Solving questions

https://www.gmatprepnow.com/module/gmat ... /video/946

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

https://www.beatthegmat.com/overlapping ... 65223.html

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

https://www.beatthegmat.com/overlapping ... 64092.html

https://www.beatthegmat.com/mba/2011/05/ ... question2
Easy Data Sufficiency questions

https://www.gmatprepnow.com/module/gmat ... /video/943

https://www.beatthegmat.com/forwhatper ... 70596.html

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

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

https://www.beatthegmat.com/eachofpeop ... 71375.html

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

https://www.beatthegmat.com/incostumef ... 69355.html

https://www.beatthegmat.com/mba/2011/05/ ... question1
Difficult Data Sufficiency questions

https://youtu.be/dsCeqF9Kbk8

https://www.beatthegmat.com/doublesetm ... 71423.html

https://youtu.be/dOZ9KM1m5Hs

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

https://www.beatthegmat.com/mba/2011/05/ ... question3
Cheers,
Brent