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Data Sufficiency


GMAT Data Suffficiency RephrasingTo score 700+ on the GMAT, test takers must develop a strategy to answer the Quant questions in 2 minutes and Verbal questions in 1 minute & 20 seconds. Data sufficiency questions can be solved well within the 2-minute mark, most likely in 1 minute and 30 seconds if the conditions and question are rephrased. Not all questions will be required to be rephrased but there are certain conditions where this technique is extremely useful, especially when concepts in Ratio & Proportion, Equations, Inequalities & Divisibility are tested.

Equations

This is the most common question type where rephrasing the conditions might be useful, especially in quadratic equations, and questions that require finding roots.

Let us look into a quadratic equation question type

For the following equations with positive roots, the value of k is greater than one

1) 3x^2 +5x + 2k = 0
2) (x+1)(3x+2) + 2k - 2 = 0

1) Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient to answer the question asked.

2) Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient to answer the question asked.

3) BOTH...

Categories : Data Sufficiency

GMAT Data Sufficiency Movie TheaterWhat was the revenue that the movie theater earned from Friday to Sunday if the occupancy rate of its three screens 1, 2, and 3 were the following?

                       Friday       Saturday     Sunday         
Screen 1           85%            90%            90%
Screen 2            65%           50%            65%
Screen 3            50%           20%            15%   

1)    There are two ticket types in each screen  – Silver and Gold, Silver sold at $35 - $10 less than Gold
2...


Q) Is the sum of all the numbers between prime numbers x and y an even or an odd number?

1)    x = 3  y = 31
2)    y is the largest two digit number, x is even

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.

Answer

To answer data sufficiency questions you don’t have to solve the problem. You just have to find the sufficient condition to prove the answer choice.

Question:  sum(x+1, x+2….y-1) = Odd or Even

Condition 1: x = 3  y = 31


Sum (4, 5,….30) = odd or Even

You don’t have to solve this but since you are aware of the sequence of numbers between x and y, the answer can be found.

Condition 1 is enough to answer the question

Condition 2: y is the largest two-digit number, x is even

The question mentions that x and y are prime numbers. Condition 2 provides two more additional information about the prime numbers.

Y is the largest two-digit number

Largest...


GMAT Data Sufficiency Process of EliminationOnce GMAT test takers have learned about the fundamental concepts tested in the exam, focus should be on saving time for each question. In GMAT, each question should be answered in just under two minutes. Data sufficiency follows a format where a question is followed by two statements, labeled as (1) and (2), and five answer choices in the format:

a) Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient to answer the question asked.

b) Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient to answer the question asked.

c) BOTH statements (1) and (2) TOGETHER are sufficient to answer the question asked, but NEITHER statement ALONE is sufficient to answer the question asked.

d) EACH statement ALONE is sufficient to answer the question asked.

e) Statements (1) and (2) TOGETHER are NOT sufficient to answer the question asked, and additional data specific to the problem are needed.

Process of Elimination techniques will allow you to complete the GMAT DS questions in less than one and half minutes.

Let us consider a few scenarios:

Statement 1 is insufficient:
...

Categories : Data Sufficiency

GMAT Data Sufficiency answer choic CGMAT test takers are more inclined to pick Answer Choice C in Data Sufficiency just as they would choose choice A in Sentence Correction. This trap in assumption is obvious to test creators, and they formulate the two statements carefully to force you to pick the wrong answer choice. Watch out for this trap and know that the following three factors influence our ability to solve GMAT data sufficiency questions.

a) Order of Reading

Rarely do we change the order in which we parse through the answer choices in a multi-choice question. It is not a problem for problem solving, reading comprehension, or critical reasoning but for Data Sufficiency, the order of reading can influence how we reach the right conclusion. Test creators subtly make us believe that Statement 1 is actually part of the question, which then changes how we interpret statement 2. Here is an example:

The two sides of the rectangle are in the ratio 4:5. What is the length of the rectangle?

Statement 1: The difference in two sides is 2
 
Statement 2: The area of the rectangle is three times the original area when the length and breadth are increased by 1 unit...


During GMAT Preparation, Critical Reasoning and Data Sufficiency sections require a great deal of adjustment compared to GMAT Reading Comprehension and Sentence correction, as the later follows a format that you have seen in Computer Adaptive Tests, undergraduate level tests, and other job interview evaluation. The linear thinking that involve variables, data substitution, rules, and logical thinking might not completely work for 700+ GMAT CR and DS sections.

Let us look at a simple example that will show how our logical minds work, and the assumptions that come into play while solving a problem. Let us look at an L-Shaped object with a 4cm and 2 cm side.


GMAT Assumption Mistakes - Figure 1
How do you divide this L-Shaped object equally? Immediately our mind will parse towards vertices that can divide this object. And as you might have guessed it, a line from Point A to the opposite vertex divides the L-Shaped object equally.

Dividing the Object into Two Equal Parts

...


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...


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.

GMAT Rectangle

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 StatisticsEven if you fear statistics by its reputation, it is one of the easiest sections in the GMAT because a standard set of questions is asked and anyone who understands the fundamentals that I shall describe will be able to ace the questions. The three most basic topics in stats are mean, mode, and median. Usually, the GMAT will go one step further into range and standard deviation.

Mean: Mean is the average. Let’s say there are two numbers: 6 and 8. The mean would be:
(6+8)/2 =14/2 =7. If you analyze the number 7, it makes sense that it is average of 6 and 8. Using the same approach, the mean of n numbers a1,a2,a3…….an would be (a1+a2+a3…..+an)/n. If you remember this formula, you should be able to do well with mean questions. We shall discuss some of the standard questions in subsequent blogs, but for right now, remember the key formula and start doing some mean and average questions from Grockit games.

Mode: Let’s say that you are given a set of numbers, such as {4,3,7,9,9,11,10}. In order to find the mode, you have to arrange the numbers in ascending...


You will encounter the following three types of Profit/Loss problems in the GMAT:

Profit/loss as percentage of Cost Price

In this case you will be given the cost price and sales price, and will be asked to simply calculate the profit/loss incurred by the seller by entering into the given transaction. This will be done by dividing the difference between the Sales Price and the Cost Price by the Cost Price. To convert the decimal into a percentage, you will multiply it by 100.

Profit Percentage = ((Sales Price - Cost Price)/Cost Price) x 100

Selling price = Z x (Cost price)

Where Z is any positive number. When Z < 1 we have a loss. When Z = 1 we have neither profit nor loss. When Z > 1 we have a profit.

Profit or Loss % = (Z - 1) x 100.

Selling price = [(Y / 100) + 1]x (Cost price)

Where Y is the profit or loss percentage. When Y < 0 we have a loss. When Y = 0 we have neither profit nor loss. When Y > 0 we have a profit.

Profit/loss as percentage of Sales Price

Sometimes the problem will be worded differently and will require the test taker to calculate...


A sizeable number of GMAT math test questions belong to the Geometry section.  Some of these questions test  a candidate’s ability to understand 2-Dimensional Geometry by asking the candidate to calculate the area, perimeter or circumference of a geometrical shape.

The following geometrical shapes are most common – Triangles, Quadrilaterals, Rectangles, Rhombuses, Squares, Circles and Trapeziums.

Triangles – A triangle represents an enclosed shape made by joining three straight lines. The area of a triangle can be calculated as follows:

Area = ½*Base Side*Height of the triangle

In this formula, the Base Side can be any side of the triangle. However, depending on the base side chosen, height of the triangle needs to be ascertained. Height of the triangle is the shortest perpendicular distance from the Base side to the height of the Apex of that triangle.  Note that the height of a triangle may need to be calculated outside the triangle, depending on the base side chosen.  

Area of Triangle
...

Categories : Data Sufficiency

GMAT Don't Contradict YourselfTrue to their name, Data Sufficiency questions ask you to determine when you will have enough information to make a conclusive decision.  In doing so, these questions can assess your ability to plan ahead for a task; to elicit an effective return-on-investment (remember, you can’t use both statements if one of them is, alone, sufficient), to find flaws with conventional wisdom, and to think flexibly. Data Sufficiency questions also strike fear and loathing in the hearts of many GMAT examinees, but hold a special place in the hearts of a select few who love the nuance that these questions permit.  

There’s a hard-and-fast rule regarding Data Sufficiency that people don’t know and use as much as they should: the statements can never contradict each other.  Knowing this, if your answers for statement 1 and statement 2 are different, you must go back and reconsider your math; as Boston GMAT tutor David says, that’s an “answer choice F”, meaning that you just effed up the math somehow.

Consider the question:

Is x...

Categories : Data Sufficiency

GMAT DS InsuffiencyPerhaps no GMAT item is as symbolic of the test as is a Data Sufficiency question.  It is an iconic question format, unique to the GMAT and true to the aims of this specific test: to reward those who show the higher-order reasoning skills that will lead to success in business.

The corporate world is full of “yes men” and “groupthink” – of the kind of inertia that leads companies to think in the same direction without considering alternate points of view.  To combat that, employers and business schools seek those who can see the entire array of possibility, and the GMAT tests for that in many Data Sufficiency problems.  Consider a problem like:

Is the product jkmn = 1?

(1) jk/mn = 1

(2) j, k, m, and n are integers

Considering statement 1 it’s quite easy to get the answer “NO”.  Using 1, 8, 2, and 4, for example, satisfies statement 1?s constraints but clearly gives a product unequal to 1.  So does 1, 20, 5, and 4.  But having just one “NO”...

Categories : Data Sufficiency

GMAT DS Obvious Answer TrapData Sufficiency questions are supposed to be hard; more so than any other question type they tend to represent a chess match between you and the author, as the author has two chances to get you to make a mistake.  She won’t likely waste either statement giving you an easy pass – the questions have to elicit something from you in terms of efficiency or ingenuity in order to answer them correctly, so if an answer choice seems obvious within 15-20 seconds and you can’t spot a trap, well, you just fell into the trap.  Consider the question:

What is the value of x?

1) 3x + 2y = 15

2)  y = (-3/2) (x – 5)

This should pretty obviously be C. 

Two equations, two variables, neither works alone but both work together, right? 

But that is too easy, and the GMAT won’t often give you the answer that quickly.  Much as though the author had moved a pawn...

Categories : Data Sufficiency

Data Sufficiency questions are not the same as your regular "Find the value of x" question. GMAT DS Questions require you to adjust in your approach to Math Problems. You are not primarily concerned with the final answer, but rather whether you have enough information to get you to that answer. For example, if you’re asked to find the value of x, and a statement tells you that 300x + 257 = 1345, you know that this statement is sufficient, because you can perform arithmetic on that equation to isolate x. Are you going to perform it? No, because it’s too complicated and you don’t need to! All you’re concerned with is whether you can find the answer.

It might strike you as odd, but because of this principle, you can tackle some supposedly difficult DS questions without writing down a single equation or calculation! Sounds too good to be true, but in actuality, it makes a lot of sense. Remember, in business school you’ll be given data in case studies, and you’ll be expected to determine relatively quickly what information is relevant. DS questions are perfect for testing this ability because you have to look at the information given to you and cut to the heart of what is most important about that information.

As an example, let’s look at this rather wordy DS problem:

...




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