Data Sufficiency Stratergy

[aseem.dhingra]

Hi

I dont know if I should put this question in the strategy section or here but here goes -:

I consistently score around 45-49 in quant and 40-42 in verbal. After browsing through these forums, I began zoning in on a more detailed analysis of my deficiency in the Quant Section. I have a tough time solving Data Sufficiency questions of a higher difficulty level ( MGMAT - 700-800 ).

How does one decide where to plug in numbers to solve a DS question or manipulate algebraic equations to get the desired result. Here's an example of what I mean -:


In the rectangular coordinate system, are the points (a, b) and (c, d) equidistant from the origin?

(1) a/b = c/d

(2) sqrt(a*a) + sqrt(b*b)= sqrt(c*c) + sqrt(d*d)

Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
Both statements TOGETHER are sufficient, but NEITHER one ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.

This question can be solved by plugging numbers and manipulating equations also. The reason I ask is because when I reach about question 20-22 of my Quant Section, all the questions require about the same reasonable time ( 1.30 - 2.30 minutes ). I rarely have enough time to try and formulate equations and if it doesnt work out, then try plugging in numbers. This's just one example but there're a lot more in the GMAT Prep question Pack 1 or the OG.

[Mike@Magoosh]

Hi there. I'm happy to add my 2¢ to your question.

What you ask is an excellent and subtle question. First of all, here's a free video that may help with choosing numbers.
https://gmat.magoosh.com/lessons/368-choosing-numbers

You're already getting 45-49 in Quant, so that implies to me that you have a reasonably strong background in math. One thing I will say is: the DS questions are designed to be solved relatively efficiently, and there's often a "key" to the problem --- with the right perspective, it's a relatively quick solution.

For example, this problem, as often for geometry and coordinate geometry problems, the visual perspective is deep and powerful. Notice --- this is neither algebraic or numeric --- it's a whole other approach. See the attached solution.

I will point out --- I love geometry and the visual perspective, and so I saw the solution to this in a flash, but in the attached pdf, it took me many words to convey clearly everything I had seen. Do not be fooled by the length of the explanation. When you translate the visual perspective to verbal form, it's always wordy, but in and of itself, the visual perspective can make sense of things in a glance.

Do not underestimate the powerful implications of geometry. I think if you are able to integrate the visual perspective as a third approach, along with algebraic and numeric, you will find yourself picking up substantially in your DS efficiency.

Does all this make sense? Please let me know if you have any further questions.

Mike

[[email protected]]

Also there is one strategy that I follow in Data Sufficiency. It is that I try everything I can and try to negate one statement that is give. If my try is to negate and if that is possible with a statement, then the argument or the statement somewhere does not hold. That means it is not airtight.

Try to negate as much as possible. Remember that the options in CR are very similar to the statements in the DS.

hope this helped you...

[aseem.dhingra]

Thanks for the comments

@ Amit

Can you explain with an example ! I didnt quite understand what you were trying to explain.