One way to quickly answer questions when you are stumped is to try to test answer choices. You are only given five, so sometimes this will get you to the correct answer faster than doing the work to multiply the problem out.

You can rent DVDs at a local video store for 5.00 per movie without a membership. However, if you purchase a membership for 7.00 per month, you can rent DVDs for 2.00 a piece. What is the minimum amount of DVDs you would have to rent to make it worth it to purchase the membership.

- (A) 1
- (B) 2
- (C) 3
- (D) 4
- (E) 5

Because this question is asking for the minimum amount, you can start testing with the lowest number and work your way up. Once you find a value where the membership costs less than the non membership, you have found your answer.

(A) with the membership its $9 and without its 5, so this isn’t our answer

(B) with the membership its $11 and without its $10, so also no

(C) with the membership its $13 and without its $15, so now we have found our answer!

The other way to have done this would have been to create an algebraic equation, set the two sides equal to each other and solve for x, then figure out the next value, like so:

7+2x=5x

7=3x

x=7/3 or 2 1/3

we could then deduce that the right answer is 3, because you can’t rent half a DVD

However, with problems like these it’s often faster to simply check answers and at the end of the day, we want to get though the problems in the quickest way possible.

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It is very important to tackle data sufficiency in a formulaic way. There are too many options to keep them in your mind all at once, so its better to methodically eliminate things until you have only one option left. The first and most important step is to flesh out the prompt, so you can gather as much information as you can from it. Additional info, which can make or break the question, is often hidden in the prompt. Take a look at this problem:

The difference between Simon and Gary’s age is twice as much as the difference between Simon and Chris’s age. If Simon is the oldest, what is the average (arithmetic mean) of all three?

(1) Gary is 27

(2) Chris is 31

If we just did this problem superficially, then we would start by putting the prompt into an equation, such that

S-G=2(S-C) which we can multiply out to get

S=2C-G

We then might conclude that we only need two of the numbers to get the average, because we know the relationship between the three, but let’s try substituting S in the average equation ((S+G+C)/3) with 2C-G.

(2C-G+G+C)/3=3C/3=C

The Gs actually end up canceling out in the equation, so that all we need to know to figure out the average is Chris’s age. Thus, going through the options is very simple. (I) tells us nothing, because we would still need Simon’s or Chris’s age, but (II) gives us all the information we need to solve. Had we not taken the time to plug the one equation into the other, we probably would have incorrectly assumed that the correct answer was that we needed both together to answer the question. However, it is now clear that we only need (II).

After you multiply out the prompt and gather all the information from that, you must then turn to your two pieced of information. I find the easiest way to do this is to go through them in order: (I) then (II) . That way you don’t get confused about what you’ve done. However, some people find it easier to start with the easier of the two options, so find what works for you and stick to it.

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Another strategy that might get you to the answer faster than simply doing the problem outright, is plugging in numbers. This might make it easier to visualize the problem and help you work through it faster. If you are struggling with a GMAT problem and are having trouble visualizing the problem, try replacing the unknowns with a value. For example, take a look at this problem.

To practice law in their state, the third year law students at Western University have to pass the bar examination. If 1/3 of the class opted not to take the bar examination and 1/4 of those who did take the test, did so and failed. What percent of the 3Ls will be able to practice law in their state?

You could try to solve this problem outright, however an easier way might be to just pick a convenient number for the class and then use it to solve the equation. It’s important to choose your number carefully and strategically. Picking 5 for this problem wouldn’t work, because you can’t even take 1/3 out of 5 evenly. A better number is one that both 3 and 4 can go into, like 12. If the class has 12 people in it and 1/3 don’t take the test, that means 4 don’t take it and 8 do. Of those 8, 2 fail, so 6 in total are able to practice. The answer is asking for the percentage, so 6/12 is 50%.

]]>Like any essay, you need an introduction and a conclusion. You should start the introduction by restating the argument in some way and then by giving a broad, general statement about what is wrong with it.

There are several ways you can structure the essay, but in general the simpler the better. Thus, I recommend one of two ways. You can either make each paragraph describe a flaw and how to improve that flaw argument, or you could make each paragraph describe a flaw and then put the improvements in the conclusion. Regardless of which one you choose, pick one and stick to it.

The conclusion should be a quick summary and include the improvements or not, depending on what structure you chose. You should not repeat things you have already said verbatim. Find a new way to say something, even if you are technically repeating yourself.

Obviously, you should start the AWA by reading the prompt. This should take you two minutes max. When reading, make sure that you identify the premises and the conclusion. Then, you should brainstorm 3-4 flaws that you find in the argument. This should take you 3-4 minutes. You will use these flaws to form your outline.

The bulk of your time should be spent writing. Follow the structure that you decided worked the best for you and try to be persuasive in your writing. Make sure that you leave a few minutes at the end to read over your essay and correct any spelling or grammar mistakes.

]]>If you are looking at a problem solving question, and thinking about tackling it in a long, roundabout way, then you are probably looking at it wrong. The questions are written in such a way that it seems like there is only an extremely complicated way of doing things, but in reality there is always a simpler way. So, before you start going into that five minute calculation stop and think about if there is a quicker way to do things.

Use what you are given, for example the test is multiple choice, so there is only a finite number of solutions to pick from. If those choices are far enough away from each other, then you may only need to estimate. Take, for instance, this problem:

What is 26% of 4/17 of 850?

- A) 24
- B) 54
- C) 88
- D) 146
- E) 290

These answers are fairly spread apart, so you don’t have to do the entire calculation, which would be unnecessarily complicated and time consuming. 26% is a little over ¼ and 4/17 is a little under 4/16 or ¼, so you can just take ¼ of ¼ of 850, which is 1/16 of 850 or approximately 53. There is no number that is anywhere near that except for B, so we know that is our answer.

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Your skills that you practice while studying for critical reasoning will help you immensely here. Every argument will have at least one flaw, probably several. You should think of the passage as if it was all true within itself and focus on how well the conclusion flows from the premises. Don’t question the facts. Question how well everything fits together. For example, if the passage states:

A study showed that 90% of people who switched from eating three meals a day to only eating one meal in the morning and one meal at mid-day, reported weight loss. Therefore, eating only two meals a day, is the best way to lose weight.

Instead of saying something like, “90% seems like and unrealistic number,” which actually does nothing to analyze how the premises follow from the conclusion, focus on questions like:

- What if they only lost weight because they ate all their meals early in the day? What if people who ate only one meal at mid-day and one in the evening reported no weight loss?
- Even if we accept that two meals a day is better than three meals a day for weight loss, does that really mean it is the best? What if there is a third and better option?

Each of these questions can then be rewritten into paragraphs to describe flaws in the argument. You can also describe how each flaw could be eliminated, which I would recommend because, in general, longer essays tend to score higher. Here is an example of how these questions a be turned into part of an AWA essay:

- The argument is flawed, because it fails to address the fact that the weight loss could have been a result of the fact that the two meals that were eaten were earlier in the day. For example, it could be true that people who ate their two meals late at night, may report no weight loss. In order to make the argument more sound, the author could specify that they mean two meals mid-day and earlier in the conclusion.
- The conclusion states that eating two meals a day is “the best way to lose weight.” However, it fails to prove this. Even if it successfully proved that eating two meals a day is better than eating three meals a day, it does not address any other methods of weight loss, so cannot state that it is the best. It could be possible that there is another, more effective option. In order to improve the argument, the conclusion needs to be adjusted to only address how two meals a day compared to three meals.

The analytical writing section, which consists of one essay that analyzes an argument, is the first thing you will see on the test. You will be provided with a prompt and then given thirty minutes to read it and write an essay analyzing the effectiveness of the argument. This section tests how well you can logically analyze and argument and how well you can persuasively write.

You are scored on a scale from 0-6, in half point increments. Your essay will be scored by two separate entities, one of which may be a computer program. The two scores will then be averaged. If they are different by more than a point, then a third reader will determine the score.

MBA admissions committees just want to know that you are capable of logically analyzing an argument and creating a persuasive response. Thus, an amazing AWA score won’t wow them into accepting you. However a very poor score (4 or below) may send a red flag. The best way to study is to get the official GMAT Write software from GMAC, or through a course, many of them provide it. If you score a 4.5 or higher on both, then I would say you are done with studying for the AWA. However, if you struggle with writing and end up scoring lower, you might want to do some additional practice.

]]>Another good strategy for DS is to test numbers. However, this strategy is not as effective if you don’t test the number strategically. For example, if you have a problem that asks if is x positive and (I) says x^{2 }< x testing only positive integers won’t tell you much about x. For example, this in untrue for all positive integers above 1, which might lead you to believe that x is not positive. However, the best way to test numbers is to test numbers that are different from each other in fraction vs. whole, positive vs. negative etc., like so:

Testing these different numbers, made us realize that the values that work for x fractions greater than 0 and less than 1, so x is in fact is positive. If you have to create a chart that makes things easier, like the one above you can do that on your notepad. You can even label them for the different aspects you need to hit, such as:

- positive whole
- negative whole
- positive fraction
- negative fraction
- 0

Its also important to pick simple numbers. If you pick overly complicated numbers, it will take you much longer to complete the calculations to test the actual numbers.

]]>Just like it is important to flesh out your prompt, it is equally important to flesh out (I) and (II) in the context of the question. Let’s look at another example:

x=y+1 what is the value of xy?

(I) x^{2 }= y + 1

(II) x = √ (y+1)

The prompt is pretty straightforward. We are looking for the value of xy and we know that x=y+1, so we can also say we are looking for y(y+1), or that if we know the value of one of the numbers, we can figure out the value for the other and thus the product.

We’ll start by going over (I), we can actually set x and x^{2} equal to each other, because they both are equal to y+1. x= x^{2 }yields two solutions for x, 1 and 0. This might lead you to think that we cannot determine what xy is. However, if we put this in context of the question we will discover that this is not the case.

If x=0, then y=-1, therefore the value of xy=0

If x=1, then y=0 and the value of xy is also 0

So, even though we don’t know the value of x, we still know the value of xy, so (I) is actually sufficient.

For continuity’s sake, lets also look at (II), which tells us that x = √ (y+1). This means that

y+1 = √ (y+1) Therefore y+1= 1 or 0 and y=0 or -1

We also know that if y=0 then x=1 and xy=0

And if y=-1 then x=0 and xy is still 0

Thus each of the options is sufficient on their own. Had we not taken the time to multiply them, out we would have gotten this question wrong.

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An important aspect to pay attention to with GMAT data sufficiency, is the constraints. When talking about constraints, I mean more than just x>0, but also the ones that are not as obvious. For example, if you are asked for a number of people, you know that it has to be an integer, because you can’t have ½ of a person. These constraints can sometimes make or break a problem. Take a look at these this example:

Bob had a planning committee meeting. The planning committee has 8 people on it and only planning committee members attended the meeting. How many people were at the meeting?

(I) Not all members of the planning committee attended this meeting.

(II) No more than one member of the committee was absent.

This problem is essentially asking you for the value of integer x and tells us that x is less than or equal to 8. (I) then tells us that x < 8 or we can be more specific and say that x is less than or equal to 7, because we know it has to be an integer less than 8. However, it is still insufficient, because it doesn’t tell us the exact number

(II) then tells us that x is greater than or equal to 7, because no more than 1 person was absent. Again this isn’t sufficient but it tells us that it has to be 7 or 8. Together, these two pieces of information tell us all we need to know. Essentially:

(I) 7 ≤ x

(II) x ≥ 7

The only option for x is then 7, so both together are sufficient. Had we not taken the time to think about the hidden constraint, we probably would have thought that the two pieces of information meant that,

8 > x > 7

Which is insufficient and would have led us to an incorrect answer.

As always, the GMAT will try to trick you by putting in subtle restraints, so it is always important to make note of them. Some ways they imply additional constraints are:

- Saying the number is an integer
- Making the numbers countable, which means they must be positive integers
- Any weight or height must be positive
- Any length is the side of a triangle square or the circumference of a circle must be positive

It is important to take note of both stated and implied restraints and utilize all of them, so that you are using as much of the information that you can.

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