GRE Quantitative Comparison Example Problem: Percent Change Problems

Testmasters helps students to increase their score on the GRE. While many students are interested in only improving their scores by a certain number of points, others want to see how their scores increase as a percentage of their original score. Such a skill also helps when solving some of the quantitative comparison questions on the GRE, which require you to know how to calculate the original value when given the percent change and the new value. One such problem is below.

If a cell phone is purchased with a contract calling and data plan, the cost of the phone is marked down 60% off its original price. Mel signs up for a data and calling plan when he purchased his phone, and he paid $300 for the phone.

Quantity A

The full cost of the phone without signing up for a data and calling plan.

Quantity B

The cost of a second phone that costs $800 without a calling and data plan.

To find the full cost of the phone for quantity A, use the percent change formula:

New Value = (100%-% Change)(Original Value)

The new value is the price of the phone after the discount has been taken, which is $300. The percent change is -60% because it is a discount and should be subtracted from 100%.

300 = (100%-60%)(Original)

Convert the percents to decimals by moving the decimal to the left twice in each value.

300 = (1-0.6)(Original)

300 = (0.4)(Original)

Divide both sides by 0.4 to find the original value of the phone for quantity A.

300/0.4=$750=Original

Compare this to quantity B, which is $800, and quantity B is larger, which makes the answer (B).

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Quantitative Reasoning: Making Ratios Rational

The GRE quantitative reasoning section contains many different types of questions, some of which can be on the difficult side, but the GRE prep experts at Testmasters are here to help you through the ins and outs of solving even the hardest of math problems on this exam.

Today, we look at ratios. Though there are many forms, most ratios are given in either fraction form or with a colon, but both forms are comparing parts to parts. The secret to most ratio problems is to first identify the total number of parts that you’re dealing with. Once that is known, you can take those parts and use the total to find fractional amounts or to solve for probability.

Here is an example of how the total in a ratio problem can help you to find a fractional amount:

A cocktail contains various ingredients: club soda, hard apple cider, brandy, and vodka. A bartender uses a ratio of 9:5:4:2 respectively to mix the ingredients by volume. How much vodka should the bartender use to prepare a 6-oz drink?

Solve this problem by first finding the total number of parts. Simply add the ratio amounts together to get the total:

9+5+4+2=20

Recall that a fraction is equal to the part over the total. The part of the mixture that is vodka is 2, and the total number of parts are 20; therefore, the fraction of the drink that is vodka is equals 1 over 10.

Multiply this fraction by the total number of ounces in the final drink to determine the amount the bartender should pour into a 6-oz drink.

equals 0.6

There will only be 0.6 oz. of vodka in a 6-oz. drink, and using this same method, you could solve for the amounts of the other ingredients, too. Try it yourself. How many ounces of club soda, hard apple cider, and brandy would each be in the 6-oz. drink? The answers are below. No peeking until after you’re done.

Answers:

Club soda:  2.7 ounces club soda 2.7

Hard apple cider: 1.5 ounces hard apple cider 1.5

Brandy: 1.2 ounces brandy 1.2

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Sample GRE Multiple Choice Math Problem – Lost in Translation

Let’s face it, your calculator is no match for my brains!

On every GRE Math section, the test makers try to come up with a few extremely difficult problems that will leave even the cleverest students scratching their heads. The really evil part, though, is that even these problems can be solved in under a minute without a calculator – if you know what to do. This means that once you “figure out the trick,” these difficult problems become easy. So, while those test makers are busy cackling with sadistic glee, let’s see if we can’t beat them at their own game.

Consider the following problem:

The average of four numbers is five less than the average of the three numbers that remain after one has been eliminated. If the eliminated number is 2, what is the average of the four numbers?

A) 17

B) 22

C) 66

D) 68

E) 100

“What numbers?” you ask, “How am I supposed to find the averages of numbers that no one knows?!”

Actually, I’ve spent the past several years building up an immunity to GRE Math.

The GRE test makers love to make math questions harder by forcing you to work with variables instead of with actual numbers. Actual numbers are concrete, intuitive, and easy to understand, while variables are more abstract and difficult to grasp. At least that’s their theory. As you’ll see, variables aren’t actually harder than actual numbers. In fact, in some cases, problems that have many unknowns can actually be faster and easier to solve than problems with actual numbers, since there is less to figure out (because there’s less you can figure out). The main trick comes at the beginning, when we have to translate the words of a problem into a mathematical expression we can manipulate on our scratch paper.

First, the problem tells us that we have “the average of four numbers.” Well, how do you find the average of four numbers? You add them up and divide by 4. We can write this down if we pick variables to represent each of the four numbers. Let’s just go with a, b, c, and d.

Here, e represents the average of the four numbers (what we are trying to find). Next, the problem tells us that we take the average of 3 of the four numbers. This mean we have to leave out one of our variables. Since d is the last one, we’ll leave it out:

The new average is represented by f. Now the problem also tells us that the variable that was left out was equal to 2, so we know that:

The problem also tells us that the average of four numbers is five less than the average of the three numbers that remain after one has been eliminated. We have let e represent the average of the four numbers and f represent the average of the three numbers, so we could rephrase this as e is five less than f:

So, now we still have all of these variables. We want to substitute variables for each other until we have one equation with one variable, because then we can solve for that variable and hopefully get closer to solving for e. Here’s one possible way to do that:

We can now substitute 3f for a+b+c in the other equation:

We can also substitute f – 5 for e, since we know that e = f – 5:

Now we have one equation with only one variable, so we can solve for f:

Of course, we are trying to solve for e, so we should plug this into the equation e = f – 5:

Thus, the correct answer is choice A. Note, however, that if you had only solved for f, 22 was a choice as well. With this problem, it’s all about translating the words into variables and then moving the variables around until you can actually solve for one of them. This problem might be a little more time consuming than some of the others we’ve looked at in this series, but it can still be solved in under a minute without a calculator, if you know what to do. So you see, with patience and practice, even the hardest problems on the GRE become easy. As you do more practice problems you will get better and better at them – the test makers tend to use the same tricks over and over again. Check back here each week for more extra hard problems and the tricks you need to solve them! Also, remember that you can find out all the tricks from experts like me with a Test Masters course or private tutoring. Until  then, keep up the good work and happy studying!

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Quantitative Comparison: Secrets of Surface Area and Volume in a Comparison Problem

It’s time to once again practice a problem for the GRE exam. This time, the professional GRE preppers at Testmasters bring you a step-by-step solution to solving surface area, volume, and quantitative comparison problems.

First, a brief note about quantitative comparison problems. For these problems, the questions can come from any area of math, but you will have to determine which quantity is larger, if both are equal, or if a relationship cannot be determined with the given information. Sometimes, you will have to calculate values for each quantity to compare them, but other times, you will not be able to find exact values because there may be variables involved. In these instances, it helps to know what happens when certain math operations are performed.

Today’s problem is a quantitative comparison problem that uses surface area and volume of a cube. The GRE does not provide any formulas, so you will have to know them before taking the exam. If you write the formulas down every time you use them, memorizing them becomes much easier.

Below are two quantities. If quantity A is larger, the answer is A. If quantity B is larger, the answer is B. If they are both equal, the answer is C, and if a relationship cannot be determined, the answer is D.

The length of a side of cube A measures 4, and the length of each side of cube B measures 3.

Quantity A

The ratio of the surface area of cube A to the volume of cube A.

Quantity B

The ratio of the surface area of cube B to the volume of cube B.

First, find the surface area of each of the cubes. The surface area is equal to sa formula. Plug in the side length for each of the cubes into the formula.

cube a sa

cube b sa

Now, recall that the volume of a cube is volume formula. Plug in the side lengths for each of the cubes into this volume formula to find the volumes of the respective cubes.

cube a v

cube b v

Because the question asked for the ratio of each cube’s surface area to its volume, divide the surface area of cube A by its volume and repeat the process for cube B.

cube a sa over v

cube b sa over v

Because the ratio of the surface area of cube B to its volume is greater than the same ratio for the surface area and the volume of cube A, the answer is (B).

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GRE Vocab and the Seven Deadly Sins: Part VII – Pride

An early sixteenth century Dutch depiction of the seven deadly sins, by a follower of Heironymus Bosch.

Finally, we come to the end of our series with the last and deadliest of the seven deadly sins: pride. While in English the word “pride” can often have a positive connotation, as in “the parents are proud of their child,” this kind of pride is something else altogether. In Latin, this sin is referred to as superbia, which perhaps gives a clearer indication of its nature than does the English equivalent. Pride is defined by the Catholic church as the belief that one is innately superior to others, especially in the sense that the sinner feels that he or she does not have to act with regard to the well-being of others because he or she is “better” than they are. Pride is thus a sin of selfishness and arrogance that leads one to feel that one is above the rules and that other people don’t matter. You begin to see why this is the worst one. According to Catholic theology, pride is the worst sin of all because it is the source of the other sins. It was, after all, pride that caused the angel Lucifer to rebel against God and become Satan, the Devil himself.

There are many excellent potential GRE vocab words that have to do with the sin of pride, including superbity, vainglory, hubris, haughtiness, hauteur, superciliousness, amour-propre, conceitedness, narcissism, and condescension. Continue reading “GRE Vocab and the Seven Deadly Sins: Part VII – Pride” »

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Quantitative Reasoning Sample: Making Percents Less Perplexing

For the GRE’s quantitative reasoning section, you will have to show your ability to work with both fractions and percents. Occasionally, problems will combine both, but because percents and fractions are closely related, even problems that use both can be solved. The GRE guides at Testmasters bring you today a walkthrough of a common type of percent and fraction problem you could see on the exam.

In an undergraduate program at a university, there were 300 graduates one year. By the time the class reunion rolled around 10 years after graduation, of those 300 students, 1 3 went on to get their masters degrees, and of those who earned a masters, another 25% continued onto higher education and got their doctorate degrees. Of the 300 original graduates from the undergraduate university program, how many had a doctorate degree at the reunion?

First, break this problem down into its components. Any time you see the word “of” in a fraction or percent problem, it indicates multiplication. Start with the initial amount of graduates and find the number who got their masters. Because the problem indicates that 1 3  of the original 300 got a masters degree, turn this into a math equation by replacing the word “of” with a multiplication sign. This makes sense, because in a fraction problem, fraction times the whole is equal to the part.

Fraction

1 3 times 300

This means that at the reunion, 100 had at least a masters degree.

Next, the problem says that of those who got a masters degree, 25% went on to get a doctorate. Rather than using 300 for the whole, the whole group in this part of the problem is the 100 who got a masters degree. With percent problems, the same formula used for fraction problems applies.

fraction part

25times100

At the 10-year reunion, 25 of the original graduates will have a doctorate.

Now, you can conquer percent and fraction problems by remembering the equations:

fraction part

Fraction

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How is Graduate School Funded?

Today we break down the ins and outs of graduate school funding!

Today we break down the ins and outs of graduate school funding!

As you’re looking into graduate school, you may be wondering “How do finances work as a graduate student? How is graduate school funded?” Well don’t worry! Today we’ll be discussing exactly that!

How are doctoral programs funded?

In general, if you are accepted as a doctoral candidate, you will receive a stipend with which to do your work. Part of this money comes from the school’s coffers, but the majority stems from your research advisor’s grant funding. This stipend won’t be a king’s ransom, and indeed you’ll likely be living at or below the federal poverty line, but you shouldn’t have to take out loans to attend a doctoral program. The exact stipend you receive varies greatly by school and especially by geographic location, but in general, you will have enough money for rent, food, and basic expenses. Many graduate students receive a roughly $22,000 stipend, which is again just enough to keep you afloat, with some beer money on the side. The important thing is you will likely not have to take out loans to attend graduate school, so though you won’t be making bank or saving a ton during these years, at least when you graduate, you will have a >$0 net worth!

Should I pay to attend graduate school for a PhD?

In general, NO. Most, if not all, reputable PhD programs are fully funded, so if you are expected to take out loans, this is a huge red flag. If a graduate program does not have enough grant funding or resources to support a graduate student, it’s likely not a very strong program. Academia is all about the research, and if the professors aren’t pulling enough grant funding to support even the most meager of graduate student stipends, they probably aren’t doing high profile work or research that would assist you in the future. Be very, very careful with pay-for-PhD programs as attending these likely won’t further your future interests!

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5 Things to Judge a Graduate Program By, Besides Academics

Here are some criteria you can use to rank the graduate programs you've applied to

Here are some criteria you can use to rank the graduate programs you’ve applied to

We’re following up last week’s post on What Graduate Programs Should I Apply to? with some more qualitative things to look at. We’ve already covered the “hard” stuff like academics and publications, so here’s some other things you should consider when looking at potential graduate sites!

  • Location: This is of course a self-evident criteria for choosing schools, but think long and hard about the area each school is located in. Do you want to live in a small college town in the southwest, or do you want to live in a more urban area on the East Coast? Are you okay with commuting with a million other people every morning, or do you want to get stuck on in an endless concrete spaghetti bowl? You’re going to be living in this location for 5+ years, so make sure you love the place!
  • Availability of collaborations: Is the school  you’re applying to a large one? Does it have many researchers in a diverse ranges of specializations? These may be questions you want to consider when narrowing down schools to apply to. Though a doctoral program will essentially have you doing your own work, it’s important to have the ability to bring in other researchers from other departments to help if necessary. Diversity is the spice of life and research as well!
  • Proximity to desired institutions: In general, if you want to work at an East Coast university post-graduation, you’ll want to attend school in that region. Just as last week’s post touched on the importance of word-of-mouth recognition, so too do we suggest that word-of-mouth is highly location-centric. A lower-ranked local graduate program is likely more respected than a marginally higher-ranked graduate program located halfway across the country. The closer you are to the institution you want to work at, the better your chances at having a leg up!
  • Local life: What kind of activities do you like doing in your free time? It’s important to promote some semblance of work-life balance, so make sure the local area fits your personality! If you like running or mountain biking, look for a school located near natural formations, and if you like being disappointed by local sports teams, make sure you choose Houston or Cleveland. Just make sure you have an ability to let off steam and find a life outside of your research. You’ll need it.
  • Cost of living: While most schools provide a stipend to live on, the distance your stipend will go depends highly on location. Rent is more expensive in San Francisco than Madison, Wisconsin, and a week’s worth of groceries in NYC might cost the same as a month’s in Charlotte, NC. You’re going to be bemoaning your lack of money in grad school anyway, but location may be the difference between crying into 1-ply tissues or 2-ply.
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