GMATClub m#03, m#17, OG12 (PS&DS)...phew.

Multiple updates are in order!
Day n-4
Did 20 PS and 20 DS questions (timed). Got a little better.
Got 2 wrong in PS and 6 wrong in DS.
Gotta re-review those damn DS questions...seems like concepts are a lot more important than I expected.

Day n-3 & n-2
Ummm...mainly partied and lazed around. I know, not good considering I have GMAT in less than a month, but :p

Day n-1
Took m#03 test from GMATClub (1st Jan 2011). Got 21/37 correct, which is terrible. But when I went through the explanations, I wasn't convince with quite a few. Need to post these on GMATClub forums and hopefully, I'll figure out why I went wrong.

Day n (today)
Took m#17 from GMATClub. Got 28/37 correct, which is a good improvement. Still need to review these.

And damnnnn! I have not put things into one single consolidated error log in very long. I really think I need to do this in order to figure what my improvement areas in Quant. Anyone want to do it for me? :) I'll pay you! Hehe...gotta rush now. So much to be done!

GMAT Love!

CP #22

GMATClub m#02 test:

Is ?

1. 
2. 

(C) 2008 GMAT Club - [t]m02#19[/t]

• Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient
• Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient
• BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient
• EACH statement ALONE is sufficient
• Statements (1) and (2) TOGETHER are NOT sufficient

Statement (1) by itself is insufficient. Consider or .
Statement (2) by itself is insufficient. Consider or .
Statements (1) and (2) combined are sufficient. The absolute values of and are equal and , implying that is positive and is negative. Therefore, is false.

The correct answer is C.

GMATClub m#02

26/37 correct on GMATClub's m#02. My percentile is 31.1% :p

Managed to finish the test on time. Some questions were pretty easy, some I answered incorrectly due to silly mistakes, and some I thought I got but apparently I didn't. Pretty good mix in terms of difficulty, although I got a little annoyed with the large number of questions from Number Properties.

Any comments on how this score is at this stage of studying? And post having worked on Time & Work (1 qs in the test - which i got wrong!), Time/Speed & Distance (0 qs. on test) and Averages/Mix/Allig (1-2 qs. on test)???

Planning & Executing

Got it, well...kind of. Alligations that it. Managed to find my old TIME notes, and went through quite a few questions from the book. Have a much better hang of averages too.

To Do:

1. Have to do some more questions from that book for DST & Work.
2. 19 tables (yes, still not done...should probably get to it NOW). FYI, learning my tables has really helped in calculating faster :) I loveeeee it!
3. Go through my FCs.

Am giving practice tests from GMATClub.com on Friday afternoon/evening and Saturday morning (free access to all tests!). So I must revise all this math stuff. Friday morning, I might do some Verbal if I have time so that my Saturday morning test can be a Verbal one.

Sunday morning (26th) is TEST DAY. Someone might lend me Kaplan practice tests, so will def give one of those.

Happy studying till then!

Absolutely Not So Simple

Tried going through GMATClub's chapter on Absolute Value, 'tried' being the key word here.
I thought it was going to simple restate that the absolute value is the distance between two points. However, it took me back to my Class XI days of trying to solve absolute value questions. Damn my sister, she's lost my theory notebook from my tuition days, and now I need to redo all the thinking for this chapter.
It's not as simple as it sounds, need to try my luck again. In other words, bhai samajh mein hi nahi aaya. Probably needs a fresh mind. If it still doesn't work, Aman Chawla to the rescue I guess.

Remainder of today's CPs.

This is the link to Remainder questions. Sriharimurthy's explanations are really good. Good questions to repeat at some later stage! Have understood them for the time being. Should probably note down what I've understood here or elsewhere, so as to not go through the whole thread all over again. Phew. I'm tired now, have solved and understood quite a few challenging questions today!

To Do:
Combinatorics tutorial from MGMAT
Kaplan questions - P&C, Probability, and all the other topics.

CP #15

From GMATClub Math Book Remainders:

If s and t are positive integer such that s/t=64.12, which of the following could be the remainder when s is divided by t?
(A) 2
(B) 4
(C) 8
(D) 20
(E) 45

OA: E

Using the concept,

If you take the decimal portion of the resulting number when you divide by "n", and multiply it to "n", you will get the remainder.
Eg. 8/5 = 1.6
0.6*5 = 3 = remainder

In our question,
0.12*t = R(remainder)
Since R has to be an integer, it must be a multiple of 0.12.
To make the calculation simpler, we multiply both sides by 100.
12*t = 100R

Now, put the value of different Rs in the equation and find which one is perfectly divisible by 12.

i.e. which one of

(A) 200
(B) 400
(C) 800
(D) 2000
(E) 4500

is perfectly divisible by 12 or 3*4.
All are divisible by 4, since they end in 00s.
Only (E) is divisible by 3 also (4+5=9).

Answer is therefore, (E) 45.

CP #14

From GMATClub:

10 business executives and 7 chairmen meet at a conference. If each business executive shakes the hand of every other business executive and every chairman once, and each chairman shakes the hand of each of the business executives but not the other chairmen, how many handshakes would take place?

(A) 144
(B) 131
(C) 115
(D) 90
(E) 45


OA: C
Chairmen shake hands 10*7=70 with business executives times. Business executives shake hands with each other 10 C 2 times or 45 times. The total is 115 .

Why 10C2?

10 business executives shakes hands with other 9 business executives in 10c2 ways = 45 ways
10c2 = 9+8+7+6+5+4+3+2+1 = 45

First executive shakes hands with remaining 9 executives
Second executive shakes hands with remaining 8 executives
Third executive shakes hands with remaining 7 executives
Fourth executive shakes hands with remaining 6 executives
Fifth executive shakes hands with remaining 5 executives
Sixth executive shakes hands with remaining 4 executives
Seventh executive shakes hands with remaining 3 executives
Eighth executive shakes hands with remaining 2 executives
Nineth executive shakes hands with remaining 1 executives
Tenth executive already shakes hands with all 9 executives.

CP #13

 From GMATClub's Probability chapter:


Q: There are 5 chairs. Bob and Rachel want to sit such that Bob is always left to Rachel. How many ways it can be done ?
Solution: Because of symmetry, the number of ways that Bob is left to Rachel is exactly 1/2 of all possible ways:
N = 1/2 * 5P2 = 10

Why half?

The Mystery of the Divisor Addition to the Negative Remainder

I have a doubt regarding the formula used for Remainders in GMATClub's Math Book: see Point #6, Eg. #2.

Q. What is the remainder of (20*27) when it is divided by 25?

Note: Rof = remainder of

A. The formula I used is: Rof xy/n = Rof {Rof[(x-n)/n] * Rof[(y-n)/n]} / n

Therefore,  Rof 20*27/25 = Rof {Rof[(20-25)/25] * Rof[(27-25)/25]} / 25
= Rof {Rof[(-5)/25] * Rof[2/25]} / 25
= Rof [(-5 * 2) / 25]
= Rof [(-10) / 25]
= (-10)

But, since the remainder is negative, we add n to it to give us the remainder.
Therefore, Rof 20*27/25 = -10 + n = -10 + 25 = 15.

Why did we add n to the negative remainder?

CP #12

Another one from GMATClub Math Book's Probability chapter.
Given that there are 5 married couples. If we select only 3 people out of 10, what is the probability that none of them are married to each other?

They have given 3 different ways to solve it. All have gone over my head. Help!

1 hr to go to office 20 kms away, 1 hr 15 mins to come back. On an avg, how much time do I waste everyday?

Finished Distance, Speed & Time from a GMATClub post. The tabular representation method is brilliant. It saved me a lot of time, since I don't have to keep writing the different forms of the formula S=D/T for every component of the question. Am definitely using the table form from now on! :-)

Also went through the post on Work problems. Didn't require much effort since my concepts are pretty clear. The only issue I have here is the time I take to solve a question, if I only rely on my concept. I will need to practice a lot of Work problems, and probably revisit my TIME notes for shortcuts. Buit I will get back to this post my diagnostic test, as the diagnostic test is untimed. Plus, there is only a limit to how much I can do in every topic over the next 2 days. Yup, probably giving the test on Saturday. Should revise everything on Friday. Phew...

Update on P&C: went through most of the solved examples in RS Aggarwal, need to wrap up Combinations with the last few questions from the book. Once this is done, need to go back to the GMATClub Math book chapter on Probability and try solving those examples I was having trouble with.

As for Remainders, still need to speak to that friend regarding the questions from the link I did not understand.

The Remainder of the previous post.

Before I forget, I also went through a post on Remainders. The formulae are easy, but when I tried solving the last question, I couldn't understand the reasoning. Also, there was a link to other questions - I had a problem grasping the reasoning there too. Need to sit down with my friend and understand all these concepts, before I can consider remainder theory finished.

The probability of my reading the new Artemis Fowl novel on the weekend is...

Went through Combinatorics and Probability chapters in GMATClub's Math Book. Combi was easy, but probability - there were some methods of solving examples that I couldn't grasp. I've done these topics in school, and I had a brilliant Math tutor who gave me pretty much all the tools required to solve questions of this type.

Am going to go through RS Aggarwal's Class XI book to revise my old way of solving these questions. Hopefully, I'll be able to solve the challenging examples from GMATClub's Math book after that.

Btw, am "working from home" today. Project is more or less done, have to put in around an hour's worth of my time on wrapping it up today. So thought it was best to stick around the house and wrap up Probability during the day...

I actually want to finish up and revise my theory by Friday evening or max Saturday, give the OG Diagnostic Test, and get to reading Atlantis Complex - the new Artemis Fowl novel! I did NOT buy it when I saw it in the book shop on Saturday, because I knew I'd want to read but I need to study now to make up for my loss of 3 weeks. Damn work!

What's your excuse? (Number Theory & Percents)

Project is almost done. Have not been able to study properly for 3 weeks I think. But I'll just put in extra effort this week and wrap it up...I hope I'll be able to!

Done with:
1. Number Theory
2. Percents
from GMATClub's Math Book.

Phew.

Also, revised Mutliplying with 2 Reference Nos. Had forgotten how to do it. Need to revise Addition Chapter.
I must repeat myself - I LOVE Bill Handley's book! :-)

Sequences & Series

Finished AP GP from GMATClub's Math Book. Since we've done AP GP quite extensively in school, concepts are pretty clear to me. It's mostly just formulae otherwise.

Putting this in here because it won't be found everywhere:

"There are some short cuts and concepts that you should know about this topic.

(1) The mean and the medium of any arithmetic sequence is equal to the average of the first and last terms.
(2) The sum of an arthritic sequence is equal to the mean (average) times the number of terms.
(3) The product of n consecutive integers is always divisible by n! So, 4x5x6 (4*5*6=120) is divisible by 3!
(4) If you have an odd number of terms in consecutive set, the sum of those numbers is divisible by the number of terms.
(5) (4) above does not hold true for consecutive sets with an even amount of terms."

Deviating from my standards

Sunday morning up with a lark,
I think I'll take a walk in the park...
Hey, hey, hey it's a beautiful day...
So, Sunday morning. And I've been up since 5. Spent about 90 minutes going through and understanding the concept of Standard Deviation. I've read it's not a common topic on the GMAT, but an 800-scorer can't afford to ignore any topic. ;-)

Went through Kaplan book's section on Averages (as suggested by 60-day Study Guide - BTG). Worked through it's practice set, which is quite simple. Moved on to Standard Deviation chapter from GMATClub's Math book. Very short. The author has posted a link to some PS and DS questions on SD which made me very happy. Till I realised they were questions from GMATPrep. At which point I quickly stopped. I want to have minimum repeat questions on my practice exams.

Did some random SD questions from GMATClub then, from non-official sources I hope.

Oh, and if you're wondering about the topic of this post - waking up at 5 for 2 straight weeks, and even on a Sunday is 3 standard deviations away from my mean! :-) (if you study the concept, you'll get it.)

My Coordinates are 28° 35' N 77° 12' E

Coordinate Geometry from GMATClub's Math Book is finito! :-)

Polygons

Finished the chapter on Polygons from the GMAT Math Book at GmatClub. :-)

Flashcard Advice

Here's my first real piece of GMAT advice I posted on a GMAT Club thread MGMAT Math Study Tips? (thread created by user "ant700gmat")

The query:

"Hey Guys,
I’m currently in the process of studying for the GMAT quant section using the MGMAT guides.
Do you have any tips on how to better remember the concepts/rules/formulas in the guides? Any advice would be helpful..
Thanks!"

My reply:

In one word, FLASHCARDS.

While you're going through a chapter, write down notes on concepts, formulas, etc. that are new to you, or you feel you need to commit to memory cos you may forget it.
Make flashcards out of these notes at the end of the chapter, to make review easier, and also to have a handy set of notes to refer to on the move.

A tip on the content of flashcards:
Convert the concept into a question, and put the answer on the back side of the flashcard. For example, if you've just learnt that 1 is not a prime number...put down "List the first 10 prime numbers" as a question, and you'll automatically cover the concept you were actually trying to recall. The reason I feel this is a better way is because sometimes, you tend to remember exactly what was written behind your flashcard, and well...it isn't really too helpful. By making a question out of it, you're APPLYING the formula/concept in a question format, which is a much better way to learn for the GMAT! Well, according to me.

The same goes for a formula. If you want to learn the area of a square, don't write "what is the formula for the area of a square?" Instead, make a question out of it. Eg. "If one side of a square is equal to 2 cms, what is the area of the square?" It's even better if you can make a question where you first have to figure out that the quadrilateral is actually a square (it's not given), and so once you figure out it's a square, you use the formula of a square's area. It will help you remember a lot of concepts, and you can have a lot of fun with it and come up with any number of questions on your own!

And yes, it is a time-consuming process (the last few flashcards I made have actually started to look like boring "what's the formula for simple interest?")...but I think it might be worth it.