Tuesday, August 31, 2010

Back with SC

I don't think I need to give reasons for my absence except for 1 word - Work.

Anyway, have started MGMAT SC Guide. Done with chapter 1, 2, 3 & 4.

Target GMAT Prep exam date: 31st October, 2010.

Thursday, August 19, 2010

OG 12 Diagnostic - Quant

Scored Excellent in both PS and DS (got 20/24 right in each). Put in my answers in the Error Log. Had to combine an error log and a guide to OG12 to make my error log make sense (will post this on GMATClub once I'm done with OG12 I guess). Apparently, my accuracy in Geometry pulled down my score. And that could be because I studied Geo a couple of weeks before the test, and managed to just put in 2-3 hours of going through my FCs on the night before the test. Still, Geo's my strong point, so not glad to see this.

Will now try the questions I got wrong once again, without looking at the actual answer (although my previous answer choice will be POEd beforehand). Once I'm done, will go through explanations of all the questions I had issues with, and fill in whatever's remaining in the error log.

Wednesday, August 18, 2010

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.

Tuesday, August 17, 2010

47 on Verbal...how do you get a 51?

She scored a 47 on Verbal. Find her debrief here.

Date of Expiry

My access to Kaplan Premier's online quizzes and tests expires on 28th August!!! :-O
I totally forgot about this...damn it! Need to do all the quizzes before it expires. Damn it damn it damn it!

Of Diagnositcs, Parties, and Plans

OG12 Diagnostic Quiz - Quantitative section: DONE.
Since I took the test untimed, it took too much time. Was exhausting. Also had to take a break between PS and DS to finish off some work that came up during that time. So on Saturday, by the time it was 4:30 in the evening, I was exhausted, mentally as well as physically. Before the test, I had managed to go through all my FCs to recall all the concepts I had learnt till then. During the test, I kept Google and my FCs handy, since I did not want to mess up a question cos I forgot a formula. The purpose of the test was just that - to gauge my level of preparedness in terms of my ability to solve a question.

Although the test went well (will put up details on my score and error log as well as CPs later), it was very tiring. Took the rest of the day off from studies - partied at night :-) and stayed over at my cousin's. Didn't look at my books on Sunday and Monday as well.

Have stayed awake post 2 on Saturday, Sunday and Monday night. This has screwed up my sleep schedule just a teeny tiny bit. Will wake up at 5 am tomorrow onwards again. Have a plan ready for the next two weeks. Aim is to give the Verbal section of OG12's diagnostic this Saturday. Not much to prepare for that really. Will start with MGMAT SC guide post that test.

28th August - first Practice test of the season (since the 2 I gave end of last year pretty much don't count now, I guess...). Should it be Princeton Review's CAT #2? Shall be followed by more partying. :-)

Oooh! Also! I'm going to get "The Power" - the new book by Rhonda Byrne. It just keeps getting better, doesn't it?!

Oh, and I guess you'd want this update too. Finally got to read Artemis Fowl's latest book. Was good fun. although I think I might have outgrown it a bit.

Thursday, August 12, 2010

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


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

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!

CP #11

This one's from the Probability chatper in GMATClub's Math Book.

If the probability of raining on any given day in Atlanta is 40%, what is the probability of raining on exactly 2 days in a 7-day period?

The way I look at it is this:
7 days, out of which on 2 it rains.
2 rain, 2 without rain = 0.4*0.4*0.6*0.6*0.6*0.6*0.6
= (0.4)^2 * (0.6)^5

However, the actual answer is
7C2 * (0.4)^2 * (0.6)^5

I don't understand why the 7C2 is required.


Went through the explanation in the chapter itself. It says that, it could rain on Day 1 and 2, or on Day 3 and 7. The sequence changes, although the number of days on which it rained remains the same. This must be factored in to get the correct answer. So other than the probability of it raining on those 2 and 5 days, we must also factor in the possibilites of different days on which it must rain.
At a preliminary level, I get it. But, I'll probably need a few more questions of the type or a different explanation to understand this thoroughly. Thoughts anyone?

Wednesday, August 11, 2010

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.

Tuesday, August 10, 2010

Calculating Combinations in Your Head

Calculating Combinations in Your Head

I had totally forgotten this! My Math tutor had taught us this in school. Thank you BTG for reminding me! :-) Very useful shortcut!!! You will NOT regret going through this video.

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!

Sunday, August 8, 2010

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.


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! :-)