5 most overlooked points while solving GMAT number based problems (Arithmetic based problems)

The 5 series!!!!

5 most overlooked points while solving GMAT number based problems (Arithmetic based problems)

1.Study the factors of a number. Factors of a numbers are numbers which can divide that number. The factors for 28 are1, 2, 4, 7, 14, 28. Factors are always smaller than a number. The number of factors for a square is always odd.

2.Study the multiples of a number. Multiples of a number are numbers which are obtained by multiplying a given number by a constant. When you want to combine two numbers use LCM. For example : What is the smallest 4 digit number which can be divided by 2,5,6,8 and 9. To solve this sum first: you would have to combine these numbers to arrive at a common number i.e.the LCM of 2,5,6,8 and 9 and then proceed to obtain the smallest 4 digit number.

3.Any number raised to the power of 4 will lead to a number (say k)whose last digit remains the same irrespective of the number of time the number is multiplied with itself.(k x k x k…..n times where n can be any integer)

4.Let a × b = c. The remainder obtained when you divide c by d is equal to the product of the remainders obtained when you divide a by d and b by d. Instead of finding the remainder of 625 when divided by 7 it would make sense find the remainder of 25 when divided by 7 and multiplying the remainder twice to get the overall remainder( 625 =25 x 25)

5.While solving number based data sufficiency problems substitution of all possible numbers (positive integers, negative integers, positive fractions, negative fractions, zero) is necessary before arriving at an answer.

For example: Is (a/b) > (c/d)
1. a > c
2. b >d

Each statement individually will not yield an answer. When the statements are taken together substitute positive numbers, negative numbers to check the consistency of the answer. Also substitute numbers which are near each other as per the number line (a=2,c=1) and numbers which are far away (a =1000, c=1)

How to take charge of you GMAT math section?

To get a high score in the GMAT, you must be familiar with the relevant concept/formula as well as the hidden relationships accompanying the concept/formula.  Many of us attempt to crack the math section of the GMAT by solving problems from sources such as the official guide.

This strategy works for people who have a strong mathematical background. For the rest of us, we have to first understand the concepts, then we have to derive relationships from the existing concepts.

Concept learning is an art. We look at a math text book and we get overwhelmed by the size. 20 odd chapters!! How am I going to master all of them? Each topic looks menacing.

But if you observe closely not all the concepts are abstract, a time speed distance problems is related to a problem based on similar triangles(geometry), a problem on roots of an equations is based on factor theorem in number system. The concepts required to crack GMAT math are inter- related.

 The quantitative section is primarily focussed on number system, ratios proportion and percentages.  Majority of the other concepts are based on these concepts. Focus on these areas first, then apply these concepts to study other concepts like Time and work, Geometry, Profit, loss and discount,.

So from 20 odd chapters the area of focus boils down to 3 or 4 chapters.

Also:  Make derivations

While working out practice problems at the conceptual level, derive notes on where you can apply the concepts. Some of these derivations are highlighted below.

Presented below are some of the hidden relationship accompanying the concept/formula. These relationships are termed ScOT bytes which are the present through out our course material.

1. Let A and B be two numbers, then Product of A and B = HCF (A, B) × LCM (A, B)

2. (Even number)^4x  will always end in the digit: ‘6’,(Odd number)^4x  will always end in the digit:  ‘1’

3. Let a × b = c.  The remainder obtained when you divide c by d is equal to the product of the remainders obtained when you divide a by d and b by d.

5. If a is increased/decreased by b%, then the new value calculated after the increase is new value = a ± b% of a  ±  (b/100) x a

7. If a same positive number is added to both the terms of ratio (of lesser inequality), then the ratio is increased.

8. If a same positive number is added to both the terms of ratio (of greater inequality), then the ratio is diminished.

9. The number of factors for a square number is always odd. For 4 there are 3 odd factors(1,2,4), for 9 there are 3 odd factors(1,3,9)...

10. Discount percentage is always calculated on  list price/marked price and not on selling price.

11.If a:b = 3:4 then a and b are not equal to 3 and 4 respectively. a = 3x and b = 4xwhere x is any constant.

12. The Simple and compound interest is the same after 1 year. The amount as well as the compound interest increases by r% every year.

Where r1,r2,r3 are interests and n1,n2 

and n3 are the years.

14. To convert km/hr into m/sec multiply the number by 5/18

15.Average speed can be calculated by 2ab/(a+b) where a and b are the two speeds. This formula is only applicable when the distance travelled is constant.

For more math tips and details browse

http://www.semanticslearning.com/beta/gmat-l3-method.asp

Download the math concept book for SAT,GMAT,GRE at

http://www.semanticslearning.com/beta/downloads/GMAT-Math.zip

Take charge of your GMAT prep

1. Study hard, no substitute for it. Study all areas of the GMAT.
2. Take notes: the areas such as math, sentence correction and critical reasoning are concept intensive and logic driven. There is a lot for you to learn from the reference sources of these areas.  Make a note of all your trouble spots: Act on them within a week. if you cant help yourself, seek a professional trainer’s help to overcome the trouble areas.
3. Always read the logic of every question that you attempt, even if the question was easy (you may find a different way of solving the question)
4. If you tend to procrastinate, first thing is to book your test date. This will help you become serious for the rest of the prep period.
5. Go through OG questions ( official guide) only after you are thorough with the concepts. Go through OG more than once. The logic of the questions, types of questions in the OG have a lot of transfer value.
6. Write practice essays at least 10 each of issue and argument under timed conditions.
7. Take at least 6 full GMAT exams( inclusive of the essays) to build stamina for a nearly 4 hr test.
8. For the first timers at least 3 months of prep time ( with the right prep no room for repeat)
9. Spend an average of 2-3 hrs per day; some of this time can be used for general reading( support for RC and essay)
10. You are good at math is not necessarily synonymous with you are good at quantitative thinking.
11. Brainstorm on as many essay topics as possible; consult experts for more ideas pertaining to abstract topics.
12. Knowledge of idioms is a must for  significant improvement in sentence correction questions.
13. Say no to hearsay: if some one says GMAT math is easy, double check, because he may have performed in the medium level test and scored not more than 580.Even the official guide doesn’t present questions of the highest difficulty possible.
14. Vocabulary is not altogether unimportant; you must know, say, the meaning of ‘condescension or laudatory’ as the author’s tone and the difference  between ‘preface’ and ‘foreword’ as the source of the passage; the emphasis is on functional diction.
15. For success in critical reasoning there is lot to learn- types of logic, nature and components of arguments; strategy for categories of questions; you get them all at the click of a mouse.
    

Access  them; make success.