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]]>Good luck!

**Numeric Entry Questions**

1. Set S consists of the integers from -1 to 5, inclusive. If N is the product of three distinct members of Set S, how many unique values of N are there?

Numeric Entry ____________

2. A combination lock has three dials, each consisting of a single digit, 0-9. The lock can be opened only if each dial is in the correct position. If the code for the lock consists of three prime numbers, what is the probability that 252 is the code? (Provide answer in fraction form).

Numeric Entry ___________

3. Twelve doctors are to be selected by hospital staff to sit on a six-person committee. Within that committee, an additional subcommittee of three doctors will be formed. How many unique sub-committees are possible?

Numeric Entry ____________

**Explanations:**

1. The quick way to this question is to think of it as a combination problem. See, when you take the product of three numbers it doesn’t matter which order those numbers are in, e.g. 1x2x3 = 3x1x2. Since there are 7 numbers and three of being chosen, you may be tempted to use 7C3. However, there is a little twist to this problem. Any product with a zero in it will result in zero. The question is asking for unique products so we will have to eliminate this possibility. Therefore, let’s use only six of the seven numbers (-1 through 5, not including the 0). So we get 6C3, which gives us 20. Then, that leaves us with a product that equals 0. And since we know that the other combination of numbers will not equal 0, we add that 1 case (where the product is zero) to the 20 other cases, giving us 21.

Answer: 21

2. Fun question! The trick is realizing that you don’t want to take the total possibilities hof a 0-9 lock with three positions. The question already gives you the following stipulation: each of the three numbers to the lock are primes. Therefore, the total possibilities are 64. Since 252 is one specific number of these 64, the chances of choosing at random are 1/64.

Answer: 1/64

3.Like the other questions above, this one also has a twist: It doesn’t matter how many doctors are chosen for the initial committee, since the three chosen for the subcommittee are ultimately taken from the twelve doctors. So all we have to do is use 12C3, which gives us 220.

Answer: 220

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]]>One of the most dread-inducing additions to the GRE—back when it changed in Aug. 2011—was the Numeric Entry question. The reason is apparent: instead of five answer choices to guide you, suddenly there is nothing more than a box, a big blank waiting for you to cough up one number out of millions (if not billions!).

But really speaking, the Numeric Entry question should not inspire such fear. Believe it or not, this question type may actually be far less diabolical than the seemingly innocuous five-answer multiple-choice question. To illustrate that this is indeed the case, let’s take a look at the following question:

*Two stacks of ten cards each are numbered 1-10 and randomly shuffled. Sam has to pick the top card from each stack and guess the number on each card. What is the probability that Sam guesses both numbers correctly?*

*.001**.025**.01**.02**.50*

The math here is pretty straightforward. There is a one in ten chance that Sam picks correctly from one stack. Therefore to find the probability that he picks correctly from both stacks is 1/10 x 1/10, which equals 1/100.

In the high-pressure environment of the test, we are prone to diving right into the answer choices as soon as we have the answer. Doing so can result in unfortunate lapses of judgment.

In this question, it is very easy to jump at (A), thinking that 1/100 is equal to .001. Of course, if you think about it for a moment, you will realize that .001 is equal to 1/1000. The problem is we don’t take that moment. And just like that, instead of choosing (C) .01, we pick (A).

Now imagine I had asked the question in the following manner:

*Two stacks of ten cards each are numbered 1-10 and randomly shuffled. Sam has to pick the top card from each stack and guess the number on each card. What is the probability that Sam guesses both numbers correctly?*

*[ ] Write your answer in decimal form. *

Now when you go to convert 1/100 to decimal form, you will take a moment to think about the conversion. The dreaded box has become your savior.

That does not mean that all Numeric questions are this straightforward. Nevertheless, you no longer have to contend with the answer traps that the GRE so craftily lays.

A few useful strategies for the Numeric Entry questions are:

- Don’t be overcome with dread.

- Read the question with the confidence that you will find the correct answer.

- If after one minute, you’ve made no discernible progress, let the question be. It is not worth spending more time hoping you will come up with the right answer. Unlike the multiple-choice, you do not have a 20% chance of randomly guessing correctly.

- Likewise, do not hover over the blank, entering in a number, then erasing it, then entering another number, then erasing it, and so forth.

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]]>Every GRE test is going to have a few math questions that are very difficult. Upon seeing them, you may become completely flustered and believe that there is no way you are able to solve such a question. Oftentimes this is not the case. Rather, you fall into any number of traps that prevent you from solving a problem that is well within your ability.

Below are five important points to keep in mind when you are dealing with a difficult GRE math problem.

It is very easy to become flustered on difficult math problems, especially word problems. One reason our normal breathing quickly changes to short, agitated breaths is we start reading and re-reading the same question over again. Hope that by the fourth read we will finally get it. At this point, re-reading is clearly an example of diminishing—and frustrating—returns. What to do?…

It often may take about 30-seconds—and a couple (and only a couple) of calm rereads of the question—to decipher a complicated math question. After all, it is complicated. Deciphering the question means understanding what the question is asking. Next, find the solution path. To do so, think—or even write down—the necessary steps to get to the solution.

A few pieces of good news: you can take longer on complicated questions. After all, there aren’t too many of them. Just make sure to solve the easy and medium questions quickly and accurately. Secondly, you can always come back to a question. Sometimes, it is easier to decode the second time around.

Sometimes a problem seems much more complicated than it actually is. The reason is we are misreading a word, or injecting or own word into the question. We spend several minutes laboring through difficult equations only to realize that none of the answer choices matches up with our answer. To avoid this **make you sure you don’t rush through the question**. Instead, read carefully, and know what the question is asking before attempting the question.

The great thing about the new GRE vs. the old format is that you can come back to questions. Sadly, many students do not take advantage of this and are unable to pull themselves from a question once they’ve bitten their teeth into it. But knowing when to unclench that jaw is very important. If a minute has gone by and you are unable to make sense of the question, move on! That question is worth the same number of points, so there is no point in wasting precious minutes on it.

The best thing about being able to come back to questions is your brain is able to make sense of the question a lot more easily the second time around. What seemed cryptic and inscrutable now seems much clearer.

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]]>The Revised GRE is a long, grueling test. To get a perfect score on the quantitative section (a 170) you will not only have to answer the difficult questions correctly, but you will also have to answer all of the easy ones. Nonetheless, I’ve focused on the difficult questions for the 170-challenge. I can’t promise a perfect correlation, but something tells me that if you can answer all five of these questions correctly in less than 10 minutes, you are well on your way to a perfect score.

Of course missing a few hardly precludes a perfect score. But make sure you learn from the ones you miss to make sure you don’t make similar mistakes in the future. And if time is a problem, remember the Magoosh GRE product has plently of questions to help you hone your chops—both from a pacing and a conceptual standpoint.

Good luck, and feel free to post your answers. Let’s see who the first perfect score will be!

1. If s and t are both primes, how many positive divisors of v are greater than 1, if v is an integer?

(A) two

(B) three

(C) five

(D) six

(E) eight

2. A quadrilateral has a perimeter of 16. Which of the following alone would provide sufficient information to determine the area of the quadrilateral. Choose ALL that apply.

[A] The quadrilateral contains equal sides

[B] The quadrilateral is formed by combining two isosceles right triangles

[C] Two pairs of congruent angles are in a 2:1 ratio

[D] The width is 4o% of the length and all angles are of equal measure

[E] If the perimeter was decreased by 50%, the area would decrease to 25% of the original

3. Product Question: Triangle in a Parabola

http://gre.magoosh.com/questions/2192

4. If x is an integer, and 169 < < 324, which of the following is the sum of all values of x?

(A) 61

(B) 62

(C) 75

(D) 93

(E) None of the above.

5. x = 350,000

y = 45,000

Column A | Column B |
---|---|

The total number of positive divisors of x | The total number of positive divisors of y |

- The quantity in Column A is greater
- The quantity in Column B is greater
- The two quantities are equal
- The relationship cannot be determined from the information given

[Note from our intern, Dylan: “I can do multivariable calculus, and got 2/5 on these in 10 minutes. These guys are tricky. :P”]

https://www.youtube.com/watch?v=BxkB8R7esB4

https://www.youtube.com/watch?v=jZdxqajkZtw

http://gre.magoosh.com/questions/2192

https://www.youtube.com/watch?v=pwzlclrvqWU

https://www.youtube.com/watch?v=–U8aDmLNzE

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]]>The post The Revised GRE– What’s New on the Math Front? appeared first on Magoosh GRE Blog.

]]>Concept-wise, I would say the math section is business as usual, save for two things: coordinate geometry and the quadratic equation.

While parabolas are tested on the current GRE, they are oddball questions, geometry outliers in the usually slew of right triangle and circle problems. In the revised GRE book, an entire section is devoted to understanding not only parabolas but also absolute value graphs (they are represented in a V-shape that can be placed in a horizontal or a vertical position. Such focus leads me to think that we’ll have a greater proportion of these questions compared to before (a good way to practice these is via SAT prep books—the SAT has many parabola questions.)

As for the quadratic equation, it is only employed to help us derive the intersection of a parabola and a line. (See page 240). Still, now that ETS is requiring us to know the quadratic equation, it is fair game for simple polynomial expressions. For instance try the problem below:

What are the two values of x that satisfy the equation above? If you haven’t learned the quadratic equation then definitely add it to your arsenal.

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