GMAT Number properties may sound scary, but they just constitute elementary mathematical principles. You probably know most of these principles by memory; if not, you could easily execute a calculation to ascertain them. The best option, though, is to study these principles enough that they seem intuitive. The GMAT Quantitative section is all about saving time; making number theory second nature will definitely save you some valuable seconds.

1.Odds and Evens

Addition

Even + even = even (12+14=36)

Odd+ Odd = even (13+19=32)

Even + Odd = odd (8 + 11 = 19)

To more easily remember these, just think that a sum is only odd if you add an even and an odd.

Multiplication

Even x even = even (6 x 4 = 24)

Odd x odd = odd (5 x 3 = 15)

Even x odd = even (6 x 5= 30)

To more easily remember these, just think that a product is only odd if you multiply two odds.

Example Question

If r is even and t is odd, which of the following is odd?

A. rt

B. 5rt

C. 6...

### How to score well in GMAT Number properties?

### How GMAT Scoring Algorithm Works?

**Categories**: GMAT Score

The GMAT is a computer-adaptive test where your score is calculated by an algorithm that provides you with harder questions (and higher score returns) when you answer previous questions correctly, and with easier questions (and lower returns) when you’ve answered previous questions incorrectly.

Through this method, the GMAT can determine your ability level in a relatively short period – **37 math and 41 verbal questions** – and provide you with an immediate score upon completion of the test. To save you the stress of trying to figure out the secrets of the algorithm, here are some important things you should know about GMAT scoring:

1) Good news: You can get a lot of questions wrong and still do well!

The job of the GMAT scoring algorithm is to determine your ability level by asking you questions that begin to close in on it. Think of how you’d play a game of 20 Questions as you attempt to zero in on the historical figure that your “opponent” has selected:

Was this person famous in the era BC? (No – too early)

Was this person famous before the Middle Ages? (No – still too early)

Was this person famous before the...

### GMAT Simple Interest and Compound Interest

Simple interest and compound interest - essential topics for an MBA. GMAC thinks the same too. So you will find these questions randomly distributed in your GMAT Exam.

Simple interest is the most basic and is a function of P, the principle amount of money invested, the interest rate earned on the principle, i, and the amount of time the money is invested, t (this is usually stated in periods, such as years or months).

The resulting equation is:

Interest = iPt

In basic terms, the above equation tells us the amount of interest that would be earned on a principle amount invested (P), for a given time (t) at a given interest rate (i).

Example

If you invested $1,000 (P = your principle) for one year (t = one year) at 6% simple interest (i = given interest rate), you would get $60 in interest at the end of the year and would have a total of $1,060.

For compound interest, you would earn slightly more. Let’s look at similar type problem, though this one involves compound interest.

...

### How to score well in GMAT Number properties?

GMAT Number properties may sound scary, but they just constitute elementary mathematical principles. You probably know most of these principles by memory; if not, you could easily execute a calculation to ascertain them. The best option, though, is to study these principles enough that they seem intuitive. The GMAT Quantitative section is all about saving time; making number theory second nature will definitely save you some valuable seconds.

1.Odds and Evens

Addition

Even + even = even (12+14=36)

Odd+ Odd = even (13+19=32)

Even + Odd = odd (8 + 11 = 19)

To more easily remember these, just think that a sum is only odd if you add an even and an odd.

Multiplication

Even x even = even (6 x 4 = 24)

Odd x odd = odd (5 x 3 = 15)

Even x odd = even (6 x 5= 30)

To more easily remember these, just think that a product is only odd if you multiply two odds.

Example Question

If r is even and t is odd, which of the following is odd?

A. rt

B. 5rt

C. 6...

### Read about Properties of Zero Before attempting GMAT Questions

**Categories**: Number Properties

The number 0 on the GMAT is tricky as its properties are the trap in to which a seemingly logical solution can lead you or are often either the key to unlocking a difficult solution. Learning the properties of zero (keep in mind that it is an even number) is a crucial skill, particularly on data sufficiency problems. Even more importantly, never forget to consider zero as a potential value for a variable, as it often produces surprising results. Consider the case of zero as an exponent:

x^0 is, by definition, equal to 1. Noting the properties of exponents can help you to prove and more easily remember this useful device: take, for example, the expression x^2 * x^-2. You could rearrange this two ways:

a) (x^2) / (x^2) --> The negative exponent moves that term to the denominator

b) x^(2-2), or x^0 --> When multiplying terms with the same base, taken to different exponents, you add the exponents

Because we can prove that (x^2) / (x^2) must be equal to 1, and that the two expressions above are...

### How to identify modifying Phrases In GMAT Sentence Correction

A common trick used by GMAT test makers is to insert modifying phrase incorrectly. Here are some sentences that incorrectly use modifying phrases:

Sentence A: Ever since her paw was crushed in the front door, Mrs. Benson has been worried about Muffin, her pet cat.

Sentence A starts off with the modifying phrase “Ever since her paw was crushed in the front door,” and then talks about Mrs. Benson and her worry for her cat. But Mrs. Benson sounds like a person, and as a person, she probably doesn’t have a paw to be crushed. It’s MUCH more likely that Muffin’s paw got crushed, causing Mrs. Benson’s worry. This sentence needs to be corrected to put the modifying phrase next to the item it modifies.

Here are a couple of ways that we can do that, depending on where the sentence’s underlining is placed:

Sentence A1: Ever since her paw was crushed in the front door, Mrs. Benson has been worried about Muffin, her pet cat.

If the modifying phrase isn’t underlined, we don’t have the opportunity to fix it-- but we can rearrange the rest of the sentence so that the thing that is modified (...

### How to practice for the GMAT without pen and paper?

**Categories**: GMAT Preparation

1. Read News Websites

News sites are great for practicing both Critical Reasoning and Reading Comprehension. Short, detail-heavy articles from The Wall Street Journal or The Washington Post make for a good GMAT-level challenge on their own. In terms of evaluating arguments, however, the real value comes from the comments on these articles that people leave online. Here you have a wonderful chance to test your CR logic skills.

As people bicker about market trends or Obama’s economic policies, you will see examples of good and bad reasoning in action. Treat them all like a GMAT excerpts. Ask yourself what their arguments rely on, and you will sharpen your ability to identify assumptions.

2. Read Opinionated Authors

Instead of re-reading the GMAT official guide for the ninth time, try...

### GMAT Sentence Correction Strategies - Focus on Testable sections

Sentence Correction questions can include up to 54 words, making for incredibly long sentences and time consuming reading. But similar to GMAT SC - Spot Decision Points, knowing what is likely to be a testable section of a sentence and what is not, you can break apart the sentence into the parts that matter to you as a test-taker. Proper nouns, correctly-applied modifiers, adjectives and adverbs can all be streamlined to make for shorter sentences.

For example, in the sentence:

Originally called BackRub, Google was founded by two Stanford PhD students, Larry Page, whose father, Dr. Carl Victor Page, was a computer science professor at Michigan State University, and Sergey Brin.

The proper nouns and excessive adjectives can be eliminated or condensed, bringing you down to:

Originally called BackRub, Google was founded by two students, Larry, whose father, Carl, was a...

### What is the greatest prime factor of 12!11! + 11!10!?

**Categories**: Number Properties

What is the greatest prime factor of 12!11! + 11!10!?

(A) 7

(B) 11

(C) 13

(D) 17

(E) 19

Solution

While it is common for students to simply look at the numbers 12!, 11!, and 10! and see that the highest naturally-occurring prime number is 11, it is important to know that this is an addition problem – the numbers 12!11! and 11!10! are combined to create a new number that may well have a higher prime factor than its factorial components.

When adding large numbers like factorials and exponents, it is often quite helpful to factor out common terms. In this case, it’s particularly important, because our entire goal is to break out the large sum into prime factors so that we can determine which is biggest. Each term has a common 11!, so by factoring that out we can get from:

12!11! + 11!10!

to

11! (12! + 10!)

Now, 12! includes a 10! – it’s essentially 12 * 11 * 10!, so we have a common 10! within the parentheses that can also be factored out, going from:

11! (12*11*10! + 10!)

to

11!10! (12*11 + 1)

At this point, the largest prime factor must be either the 11 outside the...

### GMAT Solid Geometry - Rectangular Solids and Cylinders

Rectangular Solid

Learn the concepts behind volume and surface area before you start solving GMAT Solid geometry problems. All solid geometry problems come down to this - length, breadth and height. For data sufficiency questions, look out for values of l, b and h. if any of them are missing then it would be easy to eliminate answer choices.

6 rectangular faces constitute a rectangular solid

The formulas you need to remember for a rectangular solid are

Volume = Length (l) x Width (w) x Height (h)

Surface Area = (2 x Length x Width) + (2 x Length x Height) + (2 x Width x Height)

"If length = width = height, that means that the rectangular solid is, in fact, a cube."

Terminologies

Vertex: Wow! quite a confusing word? Not really

Vertex = Corner

a) Vertex is the number of corners in a...

### GMAT Fractions - Don't get lost in the calculations

Have you wondered how writers can make a seemingly simple GMAT topic like fractions into time-consuming calculations. One strategy that GMAT test takers must adopt to simplify the calculations. For example

Dividing by 5 is the same as multiplying by 2/10. For example:

• 840/5 = ?

• 840/5 = 840*(2/10) = 84*2 = 168

Multiplying or dividing by 10’s and 2’s is generally easier than using 5’s. 90% of the time, fractions will be easier to perform arithmetic. Decimals are sometimes more useful when comparing numbers relative to one another, such as in a number line, but these questions are the exception. Even if given a decimal (or percent) looks easy, quickly convert to a fraction. Some common ones to memorize:

• 1/9 = 0.111 repeating

• 1/8 = 0.125

• 1/7 = ~0.14

• 1/6 = 0.166 repeating

• 1/5 = 0.20

• 1/4 = 0.25

• 1/3 = 0.333 repeating

• 1/2 = 0.5 repeating

Note: Multiples of these, such as 3/8 (0.375) are also important to remember, but can easily be derived by multiplying the original fraction (1/8 * 3 = 3/8 = 0.125 * 3 = 0.375)

Denominators are super important. A denominator of a reduced fraction with a multiple of 7 will not have a finite...

### Do you recommend practicing GMAT Verbal and Quantitative at the same time?

F1GMAT: Do you recommend doing Verbal and Quantitive at the same time or one after the other?

Knewton: You should study both at the same time!

Studying Verbal for a while, and then studying for Quant for a while might lead to high section scores in the short term, but this strategy is not as effective in the long run.

If mastering the GMAT were as simple as memorizing groups of facts, like memorizing all the U.S. states and then all the Canadian provinces, you could plan your studies sequentially. In fact, it would probably make sense to. However, memorization is not a big part of the GMAT (except for certain handy-to-know items like idioms and common squares): it’s much more important to build all your test-taking skills in combination.

Studying for the GMAT is like working your muscles – if you do a month of chin ups, and then a month of sit ups, the rippling shoulders and biceps you built up after the first month will have faded away by end of the second month. In GMAT terms, your Quant skills...

### GMAT Will Wear you Down: Avoid Unnecessary calculations and Don't Analyze Unnecessary Verbiage

The GMAT finds much of its competitive advantage in its ability to wear down its unsuspecting challengers, who perform unnecessary calculations on the quantitative side and reading and analyzing unnecessary verbiage on the verbal side, while all the while the GMAT packs its "knockout punch" in the form of a subtle uniqueness in the line of questioning that a tired examinee is unlikely to notice.

In order to combat this opponent, be sure to seek out opportunities to save time and energy when possible:

Quantitative Section

• When answering a Data Sufficiency question, once you know that you will get one definitive answer, you can stop performing the calculation. The actual answer does not matter, as the question is only concerned with whether you will, indeed, arrive at an answer.

• When calculating the answer for a Problem Solving question, consider the answer choices and whether an estimate, or a property of the correct value (does it have to be even? Must it be negative?) will be...

### (GMAT 800 CR Bold Faced) A leading board member of AutoSnip

A leading board member of AutoSnip Co., makers of an automated home haircutting system, recently stated that the company was in terrible shape and headed for a disastrous year. His concern was that, since the introduction of the AutoSnip III last year, calls to the customer service line have nearly doubled, indicating that people are very unhappy with the new product. Although it's true that it is the job of responsible board members to raise issues of concern, in this case the board member's analysis of the situation is mistaken. The customer service line handles not only complaints but also sales, and the majority of the new calls have been to place new orders.

What role do the two boldfaced selections play in the above argument?

A.The first provides evidence supporting the main conclusion of the argument; the second provides evidence supporting a conclusion that the argument opposes.

B. The first provides evidence, an interpretation of which supports the main conclusion of the argument; the second provides evidence supporting the main conclusion of the argument.

C. The first provides incontrovertible evidence opposing the main conclusion of the argument; the second provides evidence supporting the main conclusion of the...

### GMAT Critical Reasoning – How to solve the weakness question type?

Start solving the GMAT Critical Reasoning weaken question by reading the question first. Why? This would help you determine the task before you go into the argument.

For example:

Healica, a new drug that can cure a common disease that until now has been fatal for 50% of those infected, is made from the root of the New Zealand banananut tree. The banananut tree is rare in New Zealand, and large quantities of the root are necessary in order to make Healica. Therefore, if Healica remains in production, the banananut tree will eventually become extinct.

If true, which of the following most calls into question the conclusion above?

a) The company that holds the patent to Healica has exclusive rights to produce the drug for another 10 years.

b) Healica is expensive, and is not currently covered by most major insurance plans.

c) Banananut leaves are considered a gourmet delicacy in many parts of the world.

d) The banananut tree, although native to New Zealand, can easily be grown in other parts of the world.

e) Producing Healica is time-consuming and expensive for the drug manufacturer.

...

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