Still having a tough time with DS...

Question

It's been 2 weeks now since I started my R2 studying and I've been able to greatly improve my skills in all areas except DS. It's been so bad on my practice tests that my average is 4-6 right out of 15. Anyone else have a terrible time with DS? If so, how did you overcome it? I took the MGMAT course and have been able to apply what I learned to the other sections, but for some reason DS just isn't clicking the way I hoped it would. 

So here is my question: Since PS takes up 22 out of the 37 questions in the Q section, should I just focus on PS this week and let whatever happens with DS happen? On my last week I plan on focusing on my strengths (verbal) hoping it will raise my score and compensate (somewhat) for my Q score. I'm only aiming for a 600+ and my test date is 11/10 (a little over 2 weeks away). I aced all my Q classes in undergrad but just can't get a handle on DS. If need be, I won't have any issue taking another Q class to prove to the adcom that I can handle the workload in B-School. Too bad there isn't a DS101 class!

What do you guys / gals think?

yb · Answer

Hey Valleyball,
 Can you elaborate on your DS strategy? How does MGMAT suggest you handle them? I can then compare it to mine and tell u what does and does not work for me.
Also, I've read that DS Qs constitute half of Quant.

ValleyBall1 · Answer

Here are the strategies I use for DS:

1) I try and rephrase all the statements in the problem before I start.

2) I use the following grids:
A D
B C E

B D
A C E

I usually attack A first but definitely work with the easiest statement out of the two first.

I can usually confirm whether A and / or B is correct / incorrect but get stuck after that. For example, if I determine that A and B are not sufficient, then I know D is not sufficient either. That leaves me with C or E and that's where I usually get stuck. Sometimes my brain can't combine the two statements to make the question logical. I don't know if that makes any sense to you...or me.

I'll try and post some specific problems when I get home from work today. 

Specifically, the yes / no problems are giving me problems. I'm not really looking for a yes or no answer per se; I'm looking to see if I can get a definite (all) "yes" answer or a definite (all) "no" answer, right? If a statement renders both a yes and no (using different values, i.e., positive, negative, fractions, etc.), then the statement is not sufficient, right?

Thanks for the help! I received some PMs from members saying that I'm not alone so that makes me feel a little better. One member said that I should attack my weakness rather than give up on it. He made a good point.

The prep books all say that there are a total of 22 PS and 15 DS questions. Is that not correct?

coffeeloverfreak · Answer

For some reason, trying to work with statement 2 first really works.

coffeeloverfreak · Answer

Not always of course. And there's no REAL reason. For me, I think it was just that I'd examine statement 1, determine it was insufficient, and then move onto statement 2 but forget to check it alone, without statement 1. So I was answering C an awful lot when the answer was really B. For some reason, doing it backwards let me catch that error a lot more often.

ValleyBall1 · Answer

Makes sense. I wonder if there is a statistic out there (somewhere) that has the ratio of A:B:C answers in the OG DS section.

yb · Answer

Hey Valleyball,
 Here are a few techniques I've come up w/ for DS:

1. Try to rephrase in the context of the given statements 1) and 2). This means simplify the question which makes it easy to plug in the information given by the statements (This may be nothing new).

2. When plugging in required, make sure to test out -, +, even, odd, fraction, x>0, x<0, 0 etc. when needed. All of these will not need to be tested so use some logic to decide which are needed for the particular problem.

3. Realize that statement 2 often only adds a small, but necessary, bit of information which compliments statement 1 (or vice versa). For example, a quadratic function may yield -2,2 for 1) and 4,2 for 2). Together, you know its 2. (You have probably encountered all this, but i think its important to note that such problems occur quite frequently).

4. The DS diagrams are often drawn to confuse you, so use the info given and make ur own diagram.

5. On DS word problems, try to figure out what variables could give you what is asked for. If 1) and 2) are insufficient alone, treat them as one big word problem. Remember - whatever the number of variables in the problem, you will need the same number of equations relating at least one of the variables. It helps to translate the stem into algebra, look at the number of variables, and see if you can manipulate the equation to give you what the question is asking for. (For example, to find x-y, you need not necessarily know the values of x and y; maybe you can put them on side of the equation).

These may seem obvious but they give a good idea of how the test makers think, and in what ways they set up traps.

Hope it helps!!

coffeeloverfreak · Answer

Another frequent trap is when statements 1 and 2 give you identical information but stated differently. 

This is particularly common for problems that have two unknowns, and you're given two equations, so one would assume that together they would be sufficient. But then, both equations end up being multiples of one another, for example.

You don't need to solve all the way but you should do a few steps of work just to make sure that the info you THINK you have really exists.

ValleyBall1 · Answer

yb - I think I can use #5 immediately. I always get confused combining the two statements.

coffee - in your example, the answer would be D, not C, right? I always get this one wrong.

Thanks for the great advice! After my study session last night, I was feeling kind of low so I had to turn to The Club for some help and motivation.

I appreciate it.

Any other ideas?

coffeeloverfreak · Answer

In my example the answer would be either D or E.

If either statement alone is sufficient then it would be D.

If each statement is insufficient, given the equivalency of the two statements, the answer would be E.

ValleyBall1 · Answer

Gotcha - I should have said D or E, but that's what I meant. Did you take the GMAT already?

yb · Answer

By the way, I thought the last 50 or so DS in OG11 were good practice... (they are relatively tougher though, I got several wrong)

ValleyBall1 · Answer

Man, you can probably teach a prep course!

Congrats...

coffeeloverfreak · Answer

Thanks. But nah. Being able to DO isn't the same as being able to TEACH - a mistake lots of people make when finding a tutor and assuming they'll be good just cause they scored highly. I can often intuitively understand the answer but I'm not great at explaining how I arrived at it.

Anyway, best of luck to you!

tkkoh · Answer

My approach is similar to yb's:

1. Rephase the question into a math statement/equation/diagram. In the process, simplify/factorize/expand/etc as and when necessary - especially for "difficult" questions.

2. Circle the variables that are needed to solve the equation. This will help you to see:
a. how many variables are needed to solve the equation, and 
b. which variables are needed

The idea is to focus on the  variables  that are needed to solve the problems, and not on solving the problems themselves.

3. Then go thru the statements A & B to see if they provide the values of the circled variable(s). Most of the time, you will need to rephase the statements as well.

ValleyBall1 · Answer

Hmm, I never heard about the circle thing. I'm going to try it out tonight. Thanks tkkoh!

rahulraao · Answer

This Club is probably the greatest and coolest one around!
All you guys are really great! One guy posts his/her concern and there are so many suggestions/advices!!
Three cheers to GMAT Club and all the wonderful folks!!

ValleyBall1 · Answer

I second that. At first I was a bit skeptical about an "online club" but the intelligence of the members and most importantly, their willingness to help one another has been a pleasant surprise. A big thank you to everyone for contributing!

Paul · Answer

Great post! Keep up the good work and keep the spirit of gmatclub alive. I have been through what you guys are going through now and can certainly ascertain that gmatclub is what it is only because of its members. :good

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