Friday, September 30, 2011

5 most crucial points while solving. Permutation combinations



ARRANGMENT
N terms can be arranged in N! factorial ways, if each position can be occupied by one term.
N terms can be arranged in N^M where. Each position can be occupied by 1 term or 2 terms or …… N terms. M stands for the number of positions to be filled.

COMBINATION

M terms can be selected from P terms in PCm ways.
In certain situations it is required to first choose the terms and then arrange the terms. i.e. PERMUTATION.

Permutation = combination x arrangement.

4. When N objects are distributed among P positions such that each position can get any number of objects (zero, one, two ……N) then the number of ways of arranging the items is N+P-1Cp-1

5. When N objects are distributed among P positions such that each position can get atleast one objet (one, two ……N) then the number of ways of arranging the items is N-1Cp+1

5 crucial points while solving a probability based problem.
1. Calculate the numerator {Nos. of foverable terms} and the denominator {Total number of terms} separately using the concepts of arrangement, permutation and combination.
2. TAKE IT PERSONAL : Always imagine you are arranging / selecting the items. The action of taking the object and placing it in the relevant position is the key.
3. When two or more items are picked it is easier to compute the probability of picking one element at a time than computing the probability of picking many items at a time.
4. When A and B are selected relate the respective probabilities with multiplicataion. When either A or B is selected relate the respective probabilities with addition.
5. When the multiple outcomes are possible the probability of atleast one of them happening is computed by calculating the reverse probability = 1 – probability of event not happening.




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Wednesday, September 14, 2011

GMAT sentence correction- tips

GMAT sentence correction: Think beyond grammar
Fine, you know the GMAT SC jargon – tense error, pronoun error, subject verb disagreement. Good. Useful. But you must think beyond grammar to do justice to the range SC questions.
One of such errors is ambiguity. That is something is not clear. To make clear the meaning conveyed. So keep track of meaning also while checking a sentence for errors.
Illustration - real GMAT qns
1. Incorrect: In mammals, a lifetime’s supply of egg cells are produced during fetal development and remain dormant until maturity.

Here remain dormant is ambiguously used; one may ask what remain egg cells or development? In such cases, we need to repeat the word, cells, since these remain dormant until maturity. The verb is agrees with the singular sub lifetime’s supply.
Correct … is produced during fetal development and the cells remain dormant until maturity.

2. In 1869, anxious to balance its population of 8,000 men and 2,000 women, the Wyoming legislature extended voting rights to women in Wyoming.

A. its population of 8,000 men and 2,000 women, the Wyoming legislature
B. their population of 8,000 men and 2,000 women, the Wyoming’s legislature
C. the state’s population of 8,000 men and 2,000 women, the Wyoming legislature
D. a state population of 8,000 men and 2,000 women, the legislature in Wyoming
E. its population of 8,000 men with 2,000 women, the Wyoming’s legislature
So since you know that singular pronouns agree with singular nouns, its agrees with Wyoming legislature. But grammar alone wont rescue us here.
Look at the meaning, can Wyoming legislature have population? No the population belongs to the state, C is clear and exact. D, would mean any state’s population, not necessarily Wyoming’s.
Moral of the story
Attention to detail…is very important..keep looking out for similar errors; match grammar with meaning.







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GMAT tips to score more..

Ten ways to score poorly in GMAT! If you are rich enough for retakes, that is
1. I know math, so no need to go thru the same old arithmetic, algebra, geometry stuff
2. Tones of free downloads on your pc..what is relevant, what is not, even God may not know..
3. Just official guide, what else, nothing official about it…
4. I will join for the costliest, longest duration course in town…let them get me the score, no need to study at home..
5. I wont do the essays while practicing, only math and verbal mock exams will do
6. I speak and write good English, so verbal is going to be a cake walk, no less
7. I need just one month for preparation, after all I had high grades in college.
8. Do as many tests as possible, in fact 90 percent of my preparation time should be spent on tests. concepts? What concepts?
9. My friend said GMAT was easy for him, no tough qns ( hey, what was your friend’s score?)
10. Out of five tests I did, one test I scores above 650. So I will give the test as planned. I believe in luck!
PS Good luck

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Friday, September 2, 2011

how to tackle the Bold face GMAT Critical reasoning question


Bold face GMAT CR......not a sweat....read further

Study the example below.

Museums that house renaissance oil paintings typically store them in environments that are carefully kept within narrow margins of temperature and humidity to inhibit any deterioration. Laboratory tests have shown that the kind of oil paint use in these paintings actually adjusts to climatic changes quite well. If, as some museum directors believe, paint is the most sensitive substance in these works, then by relaxing the standards for temperature and humidity control, museums can reduce energy costs without risking damage to these paintings. Museums would be rash to relax those standards, however, since results of
preliminary tests indicate that gesso, a compound routinely used by renaissance artists to help paint adhere to the canvas, is unable to withstand significant variations in humidity.

In the argument above, the two portions in boldface play which of the following roles?

A. the first is an objection that has been raised against the position taken by the argument, the second is the position by the argument.
B. the first is the position taken by the argument the second is the position that the argument calls into question.
C. the first is a judgement that has been offered in support of the position that the argument calls into question; the second is a circumstance on which the judgement is in part, based.
D. the first is a judgment that has been offered in support of the position that the argument calls into question; the second is that position.
E. the first is a claim that the argument calls into question; the second is the position taken by the argument.

Strategy:
1. Read the overall para closely.
2. Take one bold statement at a time, analyse how this statement impacts the entire argument, including the other statement in bold.
3. Take the other statement in bold; analyse the impact of this statement in the argument in general.
4. You are not merely to establish relationship between the two statements in bold.
We can see in the above para that the first bold statement supports the second bold statement. The second statement is opposed later ( museums would be rash…) the supporting statement comes in the form of a judgment. ‘Paint is the most sensitive substance’ is a judgment, which serves as the evidence on which the claim is made.
We eliminate options B and D because the first is not the claim ( conclusion); the first is not an objection. C and D both correctly refer to the first as a judgment, but in C the second is considered a situation on which the first is based, which is an incorrect relationship. So the answer is D.