Monday, September 28, 2009

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.
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