Ratios and Proportions on the GMAT

A ratio expresses the relationship between two or more things. A proportion is a relationship that is formed by setting two ratios equal. Learn how to solve proportion problems using equivalent ratios on the GMAT….like a rockstar on this Learnboard!

Once you’ve reviewed the board, try this Data Sufficiency problem on your own:

For each month, the number of accounts, a, that a certain salesman has contracted that month is directly proportional to his efficiency score, e, which is directly proportional to his commission rate, c. What is a if c = 3.0?

(1) Whenever c = 4.0, e = 0.3

(2) Whenever c = 6.0, a = 80

Explanation:

It will be helpful to first note that because a is directly proportional to e, which is in turn directly proportional to c, a is then directly proportional to c. To say that a is directly proportional to c is just to say that there is a constant k such that ck = a, or, perhaps more simply, that there is a fixed ratio between a and c. A statement, or set of statements, will be sufficient if and only if it determines that ratio.

Statement (1): From this, the proportional relationship between e and c can be determined. However, a is directly proportional to e, and nothing is said about that relationship; therefore, the value of a when c = 3.0 cannot be found; NOT sufficient.

Statement (2): This gives you the ratio you want. You don’t need to actually calculate the value of a if c = 3.0. You just need to know that it’s possible. Don’t believe me? Because a is directly proportional to c: a/c = 80/6.0. Since the question asks for the value of a when c = 3.0, divide the numerator and denominator each be 2. a = 40. Or, if you’re determined to cross multiply: substitute the given value for c: a/3.0 = 80/6.0. By cross multiplication, 6a = 240. Therefore, a = 40; SUFFICIENT. The credited response is B.

Tricky Triangles: the GMAT’s Favorite Shape!

A triangle is a three-sided shape whose three inner angles must sum to 180°. The largest angle will always be across from the longest side. Triangles are the most commonly-tested geometry topic on the GMAT!

Remember the sum of all the interior angles in a triangle will sum to 180 degrees, so you can always solve for the third angle if you know the other two.

If you’re told two triangles are similar, the corresponding angles are congruent, or equal. You can set up various proportions to the corresponding sides as well.

More essential info:essential info: the side of any triangle must be BETWEEN the sum and the difference of the other two sides.

Check out some practice problems to refresh your triangle properties on this Learnboard!

Breaking the GMAT Word Problem Barrier!

“Expect problems and eat them for breakfast.”

– Alfred A. Montapert

Word problems on the GMAT get an unfair reputation for being especially challenging. Once you’re able to effortlessly translate the key phrases into algebra, you’ll be able to handle any word problem with aplomb!

Here’s my favorite resources from around the web all in one convenient Learnboard to help you overcome your fear of word problems: GMAT – Word Problems. And, no worries if Word Problems are the bane of your existence, we’ll start with the very basics!

Learnist: ACT Science and Data Representation

The Data Representation format on the ACT Science Test will ask you to understand and interpret information presented to you in graphs or tables. Occasionally there will also be charts, scatterplots, and diagrams.

As the video below outlines, it’s important to REALLY analyze all the data you’re given. The point of Data Rep is to determine your ability to pinpoint and extract conclusions from a series of data. 38% of the ACT Science passages will be in this format.

Making sure you have a strong understanding of the data will save you lots of headache when you read the questions. The questions will be so much easier if you spend just a few minutes focusing on the data. Check out tutor Jim Jacobson’s strategy for just how to do that in this video!

Need to see a passage in action? Sparknotes reviews some basic strategy, then shows you a passage exactly like one you’ll see on Test Day. Start with the intro, then when you get to the chart, you should glance over it to make sure that you know what’s being measured and that, in general, you feel comfortable finding information in the chart.

Now try some ACT Science Test Data Representation questions on your own on Learnist!

ACT Science Test – where to start?

On Test Day, the ACT Science Test will always be the fourth test you’ll take. It will have 7 passages and you’ll have 35 minutes to complete them. Even if your knowledge of Science is limited, you can still get a great score!

Pacing is by far the most important aspect of the ACT Science Test. Don’t wait until two weeks before your test to get started. You will only have about 5 minutes per passage, so you may want to start by only doing 5 passages, allotting 7 min per passage. Once you can confidently do 5 passages with reasonable accuracy, work your way up to 6 and then 7.

Learnist: Introduction to “Flaw” Questions on the GMAT

Flaw questions on the GMAT follow predictable patterns: the flaw usually lies in how the evidence is being interpreted, or how the evidence was obtained. No one ever said the GMAT wasn’t flawed. 🙂

This video introduces you to two of the most common logical flaws you’ll see on the GMAT: “If not P, then not Q” (double-negation) and “If Q, then P” (reverse). Be on the lookout for these in the incorrect answers of Flaw questions!

This lengthy MGMAT article covers 4 types of flaws to look out for on GMAT CR: – Confusing Percents & Numbers – Causation – Out of Scope (“Limiting” words) – Evidence/Conclusion misalign

In this sample question, we’ve got an issue with the evidence/conclusion not being focused on the same thing. The conclusion is far too general, trying to apply one instance towards an overarching rule. Notice how their focus is just not the same — we could also interpret this as being “out of scope.”

Even on a CR question, you might see a little Math! This article focuses in detail on what to do when numbers appear in Flaw questions. The important point: keep in mind that a smaller percentage of a larger number can be greater than a larger percentage of a small number.

Check out more video explanations and practice “Flaw” questions on Learnist!

Learnist: 7 Ways to Rock the GRE’s Quantiative section

Each GRE quantitative section consists of 20 questions to be completed in 35 minutes. Here’s how to get the most points possible!

When you practice for the GRE, avoid using a calculator unless you really need one. Most GRE Quant questions can be solved within 1-3 minutes without one. It’s provided on the GRE and allows for simple calculations, but don’t use it as a crutch. You should only need it for a couple of questions. You’ll save time if you can do simple conversions in your head.

Review the allowable functions here on the GRE’s official website‘s instructions for using the calculator!

Check out more ways to rock the GRE’s Quantitative section on Learnist!

Learnist: 8 Ways to Earn an Extra Point on the GRE Issue Essay

Each Issue topic on the GRE AWA section consists of an issue statement — on which you must form an opinion and write an essay in support of it in 30 minutes. Here’s how to take your GRE Issue Essay from “good” to “great”!

This Introduction to the Issue Essay video from Greenlight Test Prep covers the basics you need to know: timing, instructions, and basic strategy advice.

As the video wisely points out, there’s no “right” side — so brainstorm for BOTH before you choose the one you’d like to support. Choose the position that is the easiest to defend (i.e. the one for which you can come up with the strongest logical arguments and most specific, relevant supporting examples).

Practice makes perfect! You can best study for the GRE online by looking up the AWA prompts and practicing writing several of them within the 30 minute guideline. The only way to get comfortable with the time constraints is to practice them, so set up test-like conditions and get to work. You can see the Issue essay prompts here on the official GRE website!

Make sure you write then on the computer — a simple program like WordPad or Microsoft Word will help you mimic the test-like conditions.

Choose one side of the issue only, and don’t try to “have it both ways.” Even if you don’t believe in the side you choose, you’ll only have time to argue one side effectively. If you take a middle-of-the-road approach you won’t sound as confident or clear.

Remember, according to ETS, the “readers are evaluating the skill with which you address the specific instructions and articulate and develop an argument to support your evaluation of the issue.” What exactly you say (what side you choose to defend) is less important than how you defend it!

This article also does a great job outlining the possible types of support you can include in your body paragraphs:

• Examples
• Statistics
• Expert opinions
• Anecdotes
• Observations
• Precedence
• Consequence

You’ll probably use examples, unless you happen to already be familiar with the issue. But, remember, statistics alone won’t impress — it’s your argument skills and ability to explain how each piece of support bolsters your conclusion that will really take your GRE Issue Essay to the next level!

Learnist: 10 Tips to Rock the ACT Test this December 14th!

December 14th is the final ACT Test date of 2013. Planning to take the exam? Here’s how to focus your studies and rock the test!

Step 1 – Commit to a Study Schedule! To make sure you get the ACT test date and testing center you want, register early, at least 2-3 months before the exam. That way you can create a study schedule, working backwards from the test date. Be realistic with yourself? How much time can you commit each week to ACT practice questions? Work in 2-3 hour blocks maximum. It’s better to study 20-30 minutes a day than 4 hours once a week.

This site offers free 1, 2, or 3 month schedules! While the 3-month one is ideal, if you’re planning to take the December exam, you’ll want to modify the 1-2 month plans to fit your needs.

Step 2 – Focus on your weaknesses ASAP! Are you a slow reader? Is your ACT Math knowledge so-so? Grammar got you down? Know going in to your ACT test prep what areas need more work and plan to address them first. You’ll need more time for the weaknesses. Don’t put off studying for a section just because you dread it!

Luckily, the ACT SparkNotes website gives a great breakdown of what you’ll see on Test Day, so you can start to get a sense of what will need the most work.

Check out steps 3-10 on this Learnist board: 10 Tips to Rock the ACT Test!

Learnist: How to Conquer Pacing on the GMAT

Struggling to finish your GMAT practice tests? Not sure how much time to spend on each question? Here’s how conquer the challenge of pacing yourself on the GMAT’s 4 sections: AWA, IR, Verbal, and Quant.

Remember, there are two optional breaks on the GMAT (in between the IR and Quant sections, and in between the GMAT Quant and Verbal sections). Take them! Get up, stretch, and give yourself a mental rest!

As this post from Magoosh wisely warns, however, don’t go over the 8 minutes! The test will resume even if you’re not back in your chair! So by all means take a walk in the hallway outside the testing room, but only for about 5 minutes!

Clueless about where all that time’s going? Keep a single-problem time-log!

This MGMAT blog offers some above-average ideas for how to conquer GMAT pacing, but my favorite is the paragraphs describing the purpose of a “single-problem time-log.”

The goal of the single-problem time-log is so you can get a feel for where you’re losing those extra seconds. The “time position” column lets you know how you’re faring on average compared to idealized pacing per question for that specific question-type.

Check out more tips for How to Conquer Pacing on the GMAT on Learnist!