Random Double Matrix Question #2

by on May 9th, 2011

It’s International Double Matrix month, and as tradition has it, the 9th day is devoted to questions involving students taking or not taking certain subjects.  So, in celebration, here’s a question along with a video solution.

Don’t forget Double Matrix questions are very popular on the GMAT, so if you want a solid score, you’ll have to master them.

What’s a Double Matrix question?

For those who missed my last article, a Double Matrix question involves a certain population where each member of that population has two characteristics associated with it.  Questions that fall into this category can often be solved using the Double Matrix Method.

For an introductory lesson on the Double Matrix Method, please watch the video at http://www.youtube.com/watch?v=OWD2t5jCCZQ

Afterwards, you can try solving this harder-than-average question:

In a group of 90 students, 36 are taking History, and 32 are taking Statistics.  If 59 students are taking History or Statistics or both, then how many students are taking History but not Statistics?

A) 9

B) 19

C) 23

D) 27

E) 31

Once you’ve tried the question, you can watch the video solution below.

YouTube Preview Image


  • I felt the venn diagram approach is comparatively easy for this particular problem, for the simple reason that there is less math involved. But that could just be me :)

    P(H), P(S) and P(H union S) are given. I can derive P(H inter S) easily => 36 + 32 - 59 = 9

    Subtracting this from P(H) gives me the answer => 36 - 9 = 27

  • This is awesome approach...........

  • How can this be a 650-800 level question, i am seriously amazed as this question is a sitter in my opinion.

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