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A student has decided to take GMAT and TOEFL examinations

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Re: A student has decided to take GMAT and TOEFL examinations [#permalink]

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New post 22 Aug 2015, 05:28
Does anyone know how to solve this problem using Double-set Matrix method ?

Thanks.

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Re: A student has decided to take GMAT and TOEFL examinations [#permalink]

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New post 10 Dec 2015, 01:12
Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

A student has decided to take GMAT and TOEFL examinations, for which he has allocated a certain number of days for preparation. On any given day, he does not prepare for both GMAT and TOEFL. How many days did he allocate for the preparation?

(1) He did not prepare for GMAT on 10 days and for TOEFL on 12 days.
(2) He prepared for either GMAT or TOEFL on 14 days.

->When you modify the original condition and question, this question is frequently given on GMAT math, which is “2 by 2 question” like the table below.
Attachment:
GCDS cyberjadugar A student has decided (20151210).jpg
GCDS cyberjadugar A student has decided (20151210).jpg [ 27.69 KiB | Viewed 587 times ]

There are 3 variables(a, b, c), which should match with the number of equations. Therefore, 3 equations are needed. For 1), 1 equation, for 2) 1 equation, so we need 1 more equation. So, E is likely to be the answer. In 1) & 2),
1) Two equations b+c=10, a+c=12
2) One equation a+b=14
Based on 1) and 2), the answer is unique, which is sufficient. Therefore, the answer is C.

-> For cases where we need 3 more equations, such as original conditions with “3 variables”, or “4 variables and 1 equation”, or “5 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 80% chance that E is the answer (especially about 90% of 2 by 2 questions where there are more than 3 variables), while C has 15% chance. These two are the majority. In case of common mistake type 3,4, the answer may be from A, B or D but there is only 5% chance. Since E is most likely to be the answer using 1) and 2) separately according to DS definition (It saves us time). Obviously there may be cases where the answer is A, B, C or D.
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A student has decided to take GMAT and TOEFL examinations [#permalink]

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New post 01 Aug 2016, 17:42
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Enclosing the Matrix method solution.
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Re: A student has decided to take GMAT and TOEFL examinations [#permalink]

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New post 06 Aug 2017, 14:13
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: A student has decided to take GMAT and TOEFL examinations   [#permalink] 06 Aug 2017, 14:13

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