10 must NOT DOs for GMAT math Data sufficiency questions

The directions: 
(some tips below may require you to revisit these directions)

This problem consists of a question and two statements, labeled (1) and (2), in which certain data are given. You have to decide whether the data given in the statements are sufficient for answering the question. Using the data given in the statements plus your knowledge of mathematics and everyday facts (such as the number of days in July or the meaning of counterclockwise), you must indicate whether:

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;

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.

To understand the directions better,watch this video


Now here are some simple not do's

1. Assume that a given number is positive only

The numbers can be zero, negative fractions or decimals.
Sample question

 Is the modulus of X less than 3?
(1)  X(X+3) is lesser than 0
(2)  X(X-3) is greater than 0 When you substitute values for x, some of you usually use positive integers. you must also substitute other types of numbers like  zero, negative, fraction or decimal...

2. Assume that in a ‘Is...( refer main statement in point 1 above ) question type, no is an invalid answer. 

‘yes,’ can be a valid answer; no can be a valid answer.
You can mark A or B or C or D. 

 ‘sometimes yes and sometimes no’ are invalid.

You should mark E.

3. Ignore minimum factors required (that can be gauged from the main statement) to answer the question,

if either of the sub statements do not have the minimum factors, the answers cannot be A or B.

for example

 Is X greater than Y?
(1) X is greater than Z
(2) Y is lower than Z
We need information on X,Y to compare
Here as per directions, the answer cannot be A or B.

4. Conclude based on the outcome, while substituting a positive number to arrive at the answer.

 Check the outcome while substituting varied numbers i.e. zero,+ve integer,-ve integer,+ve fraction and –ve fraction

5. Hurriedly mark either A (or B) as the answer option when statement 1(or 2) yields an answer.

 Study statement 2(or 1)also . If this also leads to answer mark D, else mark A(or B)

6. Spend time deriving absolute values when approximation is sufficient in arriving at a decision.

You can save time by arriving at a range of possible answers than by arriving at an absolute answer

Use approximation

7. Arriving at numerical values when the question requires only counting the occurrences.

Most test takers focus on solving the equation when they see an equation. 

For example:

How many values can satisfy the equation x^2 +3x +5=0 ?

You should know that x^2 +3x + 5=0 will have two values for x (as the power of x is 2)  You need not  spend time solving this equation.  

8. Attempt a complex combinatorics problem by attempting to pick/select many objects at a time. pick/select one object at a time. This doesn’t change the final outcome.

In probability, test takers find it difficult to approach a question

For example.

what is probability of picking 3 red balls out of 10 balls in from a bag ?

You can either pick 3 balls in one go

or

you can pick one ball at a time

Either way the answer remains same.

If you focus on picking one item at a time, you will be able to arrive at a solution easily.  

9. Follow faulty logic.

i.e. A sample sum

main statement: Is the modulus of X less than 3?
sub statements:
(1) X(X+3) greater than 0
(2) X(X-3) lesser than 0

While substituting number to check the inequality always use the correct logic
Correct logic
Determine the range of numbers which satisfy the sub statements
Check whether these numbers satisfy the main statement.
Wrong logic
Determine the range of numbers which satisfy the main statement
Check whether these numbers satisfy the sub statements.

10. Ignoring additional information required to solve the problem

Sample problem
A and B takes x and y days respectively to complete a work. How many days will A and B together take to complete it?
(1) x=5
(2) B alone takes twice as many days as A alone to complete the work
additional information on the efficiency of each person’s work per day is a factor needed. If A works at 50% efficiency, A will take 10 days to complete the work.

GMAT live online verbal classes

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Topics covered:

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5 Tips to crack the sentence correction section of the GMAT.

Here are some of the GMAT sentence corrections tips i compiled.  I have added examples for each tip.

1.Check pronouns:their,his,her…..

Wrong sentence: The instructor asked everyone of the trainees to remain in their respective seat.
Correct sentence: The instructor asked everyone of the trainees to remain in his respective seat.

2. Check for pronoun omission:

Wrong sentence: In Japan elderly people are treated with far greater respect than most Western countries.

Elderly people in japan vs western countries?????

Correct sentence: In Japan elderly people are treated with far greater respect than those in most Western countries.

3. Check subject verb

Wrong sentence: A slowdown becomes useful only when the opportunity to both reorient as well as innovate are used for further growth.
Slowdown …………………………..are???

Correct sentence: A slowdown becomes useful only when the opportunity to both reorient as well as innovate is used for further growth.

4. Watch for incomplete comparisons

Wrong sentences: California’s child-support payments are as high or higher than other states.
As high…..as…..

Correct sentences: California’s child-support payments are as high as or higher than other states.

5.Watch for descriptions in the beginning

Wrong sentences: Disturbed by the media’s relentless criticism, it was decided by Gupta to resign as the chairman of TERI.
What does it refer to…….medias criticism or the disturbances

Correct sentences: Disturbed by the media’s relentless criticism, Gupta decided to resign as the chairman of TERI.


Struggling with sentence correction.. watch this video tutorial


These are some of the three dozen tips..

Click here for another sentence question with in-depth analysis
http://letsgmat.blogspot.com/2020/06/gmat-sentence-correction-question_28.html

How to prepare for GMAT critical reasoning?

Let’s face reality. Few college books prepare you to think critically. But critical thinking skills are extensively tested in both  GMAT. 

Critical reasoning (referred to also as logical reasoning or analytical reasoning) constitute an array of thinking skills that 

• involve
• analysis 
• synthesis 
• evaluation 

of numerical, verbal or non-verbal data. 

Numerical reasoning questions measures your ability to apply reasoning in a math setting whereas non-verbal reasoning involves interpreting symbols and pictures, the latter skills hardly tested in higher order aptitude tests. A majority of reasoning questions tested in these exams are text-based

(verbal reasoning).

Logic is the science of correct reasoning. It is integral to mathematics and philosophy. There are many logic concepts that originate from the above disciplines and applied in GMAT tests. 

The common test areas, viz.  critical reasoning (short passages that present arguments), argument essay and integrated reasoning draw immensely from philosophy and logic. These questions requires you to analyze issues, reason logically, and argue effectively. These skills are essential to succeed in higher studies as well as in careers.

How to build reasoning skills

1.    Using test prep resources

A common practice among test aspirants is to seek help from coaches, preparatory test guides and online discussion forums in order to learn tips and strategies to crack reasoning questions. No doubt some of these are useful sources to make you motivated and test ready. However exercise caution; desist from using these indiscriminately; do quality check.

2.    Reading varied texts

Those who are habituated to reading will over time become critical thinkers, and thereby succeed in many areas of aptitude tests. It is to be noted that the question stimulus in reasoning tests are drawn from everyday knowledge rather than from academic disciplines. Being well-read will make you familiar with the content of these problems.

3.     From principles of  logic

A third and highly productive way to build your logical reasoning is to master elementary logic theory. What is logic theory?

 Here’s a basic concept in logic.

Statement : Whenever Sara goes to the supermarket, she buys cookies.

You saw Sara this morning carrying a jar of cookies. Can you then infer that Sara has gone to the super market?

 No. this is wrong reasoning, because the supermarket is not the only place where Sara buys cookies from.

Let’s consider the scenario:  Sara did not buy cookies, can we infer that she did not go to the supermarket? Yes, we can.

In logic theory terms, the original statement can be expressed as,

If A, then B; If not B, then not A. This expression can be applied to a class of problems. Many such formulae  can be learnt and applied to logical reasoning. Merely common sense will not work.

There are many books on elementary logic suitable for beginners  that can give you solid foundation in  critical thinking. You may make use of such sources for your test preparation.

A good book on critical reasoning

One book I would recommend is Critical thinking: A Student’s Introduction by  Gregory Basham, William Irwin et al.  Online edition of this book is also available.

This book provides all basics consistent with the reasoning historically assessed in tests of reasoning and aligned with the content areas covered in  global admission examinations. Hence a good reference source for aptitude trainers too. The real-world examples and proven step- by- step approach to answering questions that this book provides can significantly improve the way you look at reasoning  problems.  The concepts that you need are; structure  and components of arguments, inductive and deductive arguments, method of evaluating arguments and  ways to spot common errors in arguments.

Let your preparation involve understanding the logic behind problems and not merely seeking solutions.

Becoming a critical thinker is both an adventure and  hard work.   Practice. Make mistakes. Learn from them. Improve. In the coming  test season, be equipped with a workable set of thinking tools.

GMAT math thinking skills 3

Topic: Number system

Difficulty level: Average

You will get word problems like this in your exams.

The concepts involved in this problem are

1. Equations

2. Numbers system

Method 1:

This method will take time as you need to read the question,  write equations, and solve them. Time consuming!!

First: assume variables

Let John’s age (at the time of the wedding) be J and Mary’s age (at the time of the wedding) be M. 

Second : write equations

The condition relating their ages is

Hence Mary was 18 and John was 24, when they got married 

That was long and time consuming.

Now let us  try approach 2

Method 2:

The previous approach involves equations. Some of us

• don’t like solving equations
• tend to make errors while solving equations..

There is an easier and faster approach  

Lets observe equation 1

M =(3/4)J                      Re-arranging ............(M/3) = (J/4)

we can observe that ages are integers. 

We can say that M is divisible by 3 and J is divisible by 4.

Similarly   

Lets observe equation 2

12 years hence

(M+12)/5 =(J+12)/6

(M+12) is divisible by 5 and (J+12) is divisible by 6

Let us use the answer options and eliminate the wrong options

Mary’s age when she got married should be one of the 5 options

(A) 24       (B) 26         (C) 18        (D) 30          (E) 22  

Mary’s age,when she got married, should be divisible by 3

Hence we can eliminate option B,E as these numbers are not divisible by 3

Further 

Mary’s age, after 12 years, should be divisible by 5

Let us take each option

 Option A: Mary’s age initially 24……after 12 years………. Mary’s age = 36

 Option C: Mary’s age initially 18……after 12 years ………Mary’s age = 30

 Option D: Mary’s age initially 30……after 12 years …….. Mary’s age = 42

Only 30 is divisible by 5

Hence option C should be the correct answer

Therefore, Mary’s age at the time of her wedding should be 18.

Isn't the second method easy and fast… However many test aspirants don’t observe these subtleties.

Most of us start writing equations when we see word problems.

Take-away:

observe the numbers, check the nature of the numbers( prime/odd/even/ divisible by x numbers….)

Watch this tutorial video and understand mathematical reasoning skills..

You can excel in math once you learn these skills.

Need math help: Get in touch with me:

My linkedin profile: https://www.linkedin.com/in/georgeanand

My facebook learning group:  https://www.facebook.com/groups/semanticsGMAT

My company: http://www.semanticslearning.com/

Want to explore math reasoning skills further try another problem

Click here

Solution here:

https://letsgmat.blogspot.com/2020/06/gmat-math-thinking-skills-1.html

Are you a quant person?

Are you a quant person?

Quantitative thinking ( thinking with numbers) is integral to corporate business careers. Hence MBA entrance tests contain a generous dose of quantitative problems. One’s performance in such problem solving is a manifestation of his overall problem solving ability.

Business Schools perceive quantitative scores as indicative of higher order thinking and decision making skills. They believe that quant thinkers can handle diverse business challenges. They can analyse, diagram, hypothesise, set goals, try permutations and combinations, perceive probabilistic outcomes and synthesis a possible outcome.

Quantitative personality is not necessarily a hardcore math person
For a quantitative thinker, math knowledge is one of the many tools in his quest for excellence in problem solving. It is also possible that one is a good quantitative person but not a math person.
By and large, a quant person is someone who can look at independent ideas and facts, look at a situation and be able to come up with a response irrespective the accuracy of the approach and thereby the solution.  It also means looking at a situation and draw up on one’s own repertoire of tactics for a possible way forward…. a possible answer... In short, a quant person  might have a great memory but is rather someone who reasons very well.

A quant person uses thinking skills approach to problems
So when a quant person looks at a math problem with varied factors, and probably requiring more than one mathematical concept, he  doesn’t get confused; he will pull the question apart and can see where one step leads into the other and can merge and manipulate the combinations to get the final answer. He goes beyond the given data, creates a problem field, assumes himself to be part of the problem, takes various experiences and knowledge points to extrapolate a position and direction. In other words, a quant person is empowered to handle problem situations well; one who says no ‘can’t’, until he has exhausted all possible knowledge, theories, and experiences before asking for help.

A quant person ‘transfers learning’
For a quant person, the idea of doing a lot of problems stems from the need to see the various possibilities of solving problems rather than an expectation of chancing upon an exam like problem. For effective ‘transfer of learning’ making observations while attempting a problem is the key.

The quant person in a nut shell should be inquisitive, innovative, fearless, flexible and an inherent risk taker.

 “the Science of Thinking” methodology attempts to inculcate quantitative reasoning in addition to quantitative aptitude in test aspirants.

GMAT math thinking skills 2

Topic: Geometry

Question Type: data sufficiency

To understand directions watch this video

The question is

What is the area? we need a numerical answer. We need some numbers to work with.

Statement 1:  AG:GE = 2:1, A ratio. No numbers. Hence not sufficient

Statement 2: AB = 10 BC= 20. Do we know the nature of the triangle (equilateral or isosceles?) no

We know that AD and BE are the two medians. The medians bisects the base into two equal parts.

The median bisects the triangle into two smaller triangle with equal areas.

 Area of triangle ABD = Area of triangle ADC

Also area of triangle ABE = Area of triangle BEC

G is the centroid so the AG: GD = 2:1 and BG:GE = 2:1

Nothing further can be arrived at. Hence statement 2 is insufficient

Let us combine both statements .. You should know what apollinius theorem is

GMAT Data sufficiency rules

Understand GMAT data sufficiency. 

There are 31 Quant questions in the GMAT.

You will get  9 to 11 data sufficiency questions

The first thing to do with a Data Sufficiency question is to learn the meaning of the options 

The answer choices are the same for every Data Sufficiency question. Therefore, you need not read the directions in the exam. You can save time... 

Watch this video and understand the directions....

 

GMAT sentence correction question - multiple errors in a sentence

Can you spot the different #GMAT sentence correction errors...

In 1974 a large area of the surface of Mercury was photographed from varying distances, which revealed a degree of cratering similar to that of the Moon’s.

(A) which revealed a degree of cratering similar to that of the Moon’s
(B) to reveal a degree of cratering similar to the Moon
(C) revealing a degree of cratering similar to that of the Moon
(D) and revealed cratering similar in degree to the Moon
(E) that revealed cratering similar in degree to that of the Moon

The intended meaning of the sentence is as follows
a large area was photographed and analysed. From that analysis the degree of catering of mercury was compared to that of the moon.

Elements that can be identified
1. Usage of a pronoun which
2. comparison..- degree of catering of mercury vs degree of catering of moon.
3. 2 clauses - A comma after distances.

Option A
Which is a pronoun . Its antecedent is Distance. Did  distance  reveal anything.. No.. Option A is ruled out.

Option B
Degree of catering of mercury is compared to moon.. That comparison is absurd. The correct comparison is Degree of catering of mercury and degree of catering of moon. Option B has an error

Option C
Revealing is a participle. The participle phrase - Revealing.... is predicated of the main subject - large area of surface. The large area  was revealing information via a photograph. The sentence structure is precise and unambiguous.  The comparison is appropriate. "That of" indicates a feature of moo. The comparison here is between feature of mercury(Degree of cratering) and feature of moon.

Option C is correct.

Option D
And indicates. that large area revealed two features.  From the intended meaning, only one feature, degree of cratering, is mentioned. Also a comparison error. ( same as option B)  Hence Option D has a multiple errors.

Option E
Which noun does "that" refers to?  Large area or photograph ?? It is not clear.  Option E is elliminated

Hence option C is the correct answer.

Hope you noticed all the errors.

If you would like to attend 20hr verbal foundation course for GMAT..contact me.. 

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GMAT math Thinking skills - 1

There are two ways to solve this problem

Approach 1 - 

This approach would require you to assume variables,write equations and solve them.

Yes!  this approach take some time

Those of you who are new to math, would, most likely, attempt a question using this approach

First :

Convert the ratio into number by introducing a constant x

The speed of the 3 runners will be 3x,4x and 5x.

Second 

Assume the distance traveled by each runner is 60 units ( 60 is the LCM of 3,4,5. You can take any number.. I took the LCM to avoid decimals.)

Speed = distance/time. Hence   Time = distance/speed

Time will be 60/3x,60/4x,60/5x. respectively = 20/x,15/x,12/x

Remove (1/x) and then you can write the numbers in a ratio: 20:15:12

Approach 2:

If you solve a mathematical question using this approach, it means you are comfortable 

• determining the nature of numbers,
• identifying  relationships between variables 
• substituting values to arrive at an answer fast

This approach would take less time than approach 1.

Now lets solve this question using this approach

You would have observed the following in the question

• ratio of the speeds are given
• distant is constant

The relationship between  speed and time is : Speed is inversely proportional to time. 

Hence if speed increases time decreases and vice versa. 

The speeds are in the ratio 3:4:5. 

Hence the times should be in the ratio: 1/3 :1/4: 1/5 as speed is inversely proportional to time. 

Multiplying with LCM (4,3,5) i.e. 60 ..............to normalize the ratio

We get 20: 15:12

The answer is 20:15:12

Take-away:

Always observe the hidden relationship between numbers

Watch this tutorial video and understand mathematical reasoning skills..

You can excel in math once you learn these skills.

Hope you understood both the methods.   

Need math help: Get in touch with me:

My linkedin profile: https://www.linkedin.com/in/georgeanand

My facebook learning group:  https://www.facebook.com/groups/semanticsGMAT

My company: https://semanticslearning.com/

Want to explore math reasoning skills further try another problem

Solution here

https://letsgmat.blogspot.com/2020/07/gmat-math-thinking-skills-3.html

8 ways to score poorly in the GMAT

Here are the top 8 ways to score poorly in the GMAT.

1. I know math,

 so no need to go through the same old arithmetic, algebra, geometry stuff. 

It is possible to get Q51 in the math section, provided you are thorough with the math concepts and you have the essential problem solving skills, which can help you crack a question in less than 30 seconds. 

2. I have tones of free downloads 

..what is relevant, what is not, even God may not know..

The cost of finding,collating and structuring free content is high.  What works for you? what doesn't work for you? Do you want to do a trial and error approach to see which plan works? 

3 . Just official guide (OG), 

what else, nothing official about it…

First build concepts, then apply the concepts on OG questions. You need to use OG at the last stage of your preparation.

4. I will join for the costliest, longest duration course in town…

let them get me the score, no need to  study at  home..

There is a popular saying : "You can lead a horse to water but you can't make it drink." 

You need to work with the GMAT tutor in tandem. Then you can maximize your score in the shortest possible time

5. I won't do the essays while practicing,

Only math and verbal mock exams will do....

Work on all the sections of the exam. The skills in the various sections ( Integrated reasoning,math,verbal. and essays) are inter-related.

6. I speak and write good English, 

so verbal is going to be a cake walk, no less

I hear this often. Only when you go deep into verbal section. You will understand the nuances. Fortunately you can get 100% accuracy in the verbal section.

7.  I need just one month for preparation,

......... after all I had high grades in college.

High grades in college doesn't guarantee you a 700+ in the GMAT. Follow the customized study plan given by the tutor. Only when you achieve the learning objective at the concepts stage, take mock tests. Only when you reach your target score in the 3 or more tests.. book for the exam.

8. Do as many tests as possible,

 in fact 90 percent of my preparation time should be spent on tests. concepts? What concepts?

Fundamentals first... ..always

Also  some notable mentions

9. My friend said GMAT was easy for him, no tough questions 

hey, what was your friend’s score?

Each test aspirant is different,  What works for your friend, may not work for you.. Get a customized study plan

10. The luck factor

Out of five tests you did, one test you scored above 650. So you will give the test as planned.  you believe in luck!

I wish life was as simple as that....

A little bit about me.

I am George, a GMAT tutor, since 2008. I coach students online as well as offline at my center. You can

• Check my linkedin profile: https://www.linkedin.com/in/georgeanand
• Join my facebook online learning community: https://www.facebook.com/groups/semanticsGMAT
• Visit my website to know about my classes:  http://www.semanticslearning.com/
• Read my thoughts on GMAT prep via my blog: https://letsgmat.blogspot.com/