CP #3

Another good question. They haven't posted the answer yet.

MGMAT Challenge Problem of the Week

10/26/09

Machines A, B, and C

Machines A, B, and C can either load nails into a bin or unload nails from that bin. Each machine works at a constant rate that is the same for loading and for unloading, although the individual machines may have different rates. Working together to load at their respective constant rates, machines A and B can load the bin in 6 minutes. Likewise, working together to load at their respective constant rates, machines B and C can load the bin in 9 minutes. How long will it take machine A to load the bin if machine C is simultaneously unloading the bin?

(A)	12 minutes
(B)	15 minutes
(C)	18 minutes
(D)	36 minutes
(E)	54 minutes

I think the answer is C. I don't think my method is long, but I do think I took a little extra time to think up of the process (again, cos I doubted my concept clarity a little, and so didn't quickly start to solve it the way I was thinking...tried applying formula first, but what good is that if I don't know the concept extremely well?). I'll wait till tomm for them to give the right answer, as well as their explanation. Then I'll compare my answer with theirs. 

Edit: The OA is C.

Much Ado about Nothing...

So, no. Nothing has been happening. Haven't been able to go through GMATPrep questions. Which sucks. And no studying has been happening. Too much other stuff to do.
Anyway, hopefully by tomm I will post something substantial about my studying.
For today, here's a very, very useful link!
The GMAT Club Guide to The-Official Guide-for GMAT Review, 12th Edition

CP #2

Wicked question by MGMAT this week! Check it out...


MGMAT Challenge Problem of the Week

10/19/09

Question

If a, b, and c are positive integers, with a < b < c, are a, b, and c consecutive integers?

(1) 1/a – 1/b = 1/c

(2) a + c = b² – 1

(A)	Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
(B)	Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
(C)	BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
(D)	EACH statement ALONE is sufficient.
(E)	Statements (1) and (2) TOGETHER are NOT sufficient to answer the question asked, and additional data are needed.

Answer

The question can be rephrased "Is b = a + 1 and is c = a + 2?"

One way to approach the statements is to substitute these expressions involving a and solve for a. Since this could involve a lot of algebra at the start, we can just substitute a + 1 for b and test whether c = a + 2, given that both are integers.

Statement 1: SUFFICIENT.
Following the latter method, we have
1/a – 1/(a + 1) = 1/c
(a + 1)/[a(a + 1)] – a/[a(a + 1)] = 1/c
1//[a(a + 1)] = 1/c
a² + a = c

Now we substitute a + 2 for c and examine the results:
a² + a = a + 2
a² = 2
a is the square root of 2. However, since a is supposed to be an integer, we know that our assumptions were false, and a, b, and c cannot be consecutive integers.

We can now answer the question with a definitive "No," making this statement sufficient.

We could also test numbers. Making a and b consecutive positive integers, we can solve the original equation (1/a – 1/b = 1/c). The first 4 possibilities are as follows:
1/1 – 1/2 = 1/2
1/2 – 1/3 = 1/6
1/3 – 1/4 = 1/12
1/4 – 1/5 = 1/20

Examining the denominators, we can see that c = ab. None of these triples so far are consecutive, and as a and b get larger, c will become more and more distant, leading us to conclude that a, b, and c are not consecutive.

Statement 2: SUFFICIENT
Let's try substituting (a + 1) for b and (a + 2) for c.

a + a + 2 = (a + 1)² – 1
2a + 2 = a² + 2a
2 = a²

Again, we get that a must be the square root of 2. However, we know that a is an integer, so the assumptions must be false. We can answer the question with a definitive "No," and so the statement is sufficient.

The answer is D: Each statement is sufficient.
--------------------------------------------------------------
The first option required just a little more calculation that the second.
I did get the answer on my first try, but I still wanted to post it here because the logic that struck me while trying to solve it may not have struck me at another point of time. I know I've opened my mind to newer ways of solving questions. Earlier, even if the idea would've struck me, just knowing it was a little bit more complicated than what I'm extremely comfortable with, I would've confused myself. Now, I take a deep breath, try to understand why I'm thinking that way, and the answer comes. Even if it doesn't, atleast I'm aware of the logic I used! I should be thanking the people at T.I.M.E classes for this. The Math teacher in Delhi (Kailash Colony) as well as Bombay (Charni Road) were pretty damn good. And they have helped me think of Math in a simpler, clearer manner, and I think I'm getting over my fear now, and beginning to not underestimate myself.
I think I've left my notepad at home. I should write my thought process here.

Plan of Action

Math - IMS BRMs, that CAT Math book for Number Systems, Time,Speed&Dist - TIME. Probability,P&C-tuition notes and class XI qs. Note: Make notebook of qs. u found challenging, and make FCs of new concepts. (1 week)
Once this is done, do PR Math Bin 4 under timed conditions. Then, do questions you got wrong from PR Bin 3. Note: Keep error log (different from book of tough qs from above) (3 days)
Now, give math diagnostic from ...GMATClub maybe? (1 day)
Proceed to DS qs. from TIME Material first (randomly select qs. from appropriate topics-arnd 50-60 qs) (3 days). Then, do PS qs. from OG11 - all questions (yes, you HAVE to do OG now)

Verbal.
CR:
Analyse what went wrong in GMATPrep, do all PR CR qs (2 days), then do MGMAT CR guide (3 days), and then do LSAT qs. (2 days) Finally, do OG11 CR qs -all of them.

SC:
Again, see what sort of problems I had on GMATPrep. Go through MGMAT SC. Do a few PR Bin 3&4 SC questions after each chapter, keep error log on qs I don't get. Do MGMAT FCs (1 week). Finally, get to OG11 SC qs. - all qs.

RC:
Do PR Bin 3&4 qs. (2 days) Then do OG11 qs. - all qs

I didn't do anything GMAT related yesterday. Updated my CV, and rearranged its format, which took about 1.5 hours! Totally worth it though. It's so much better now! Will go through wrong ans. on gmatprep today.

Practice Test #1 (GMATPrep #1)

 Two things I'm very proud of completing:
1. Finished CR review from PR yesterday. Finally! :)
2. Gave GMATPrep 1 a couple of hours back.
Also went through Math review from GMATPrep software and no, there was nothing new on it, which was disappointing.
Anyway, so got a 620. Which I guess isn't that bad with this amount of prep.

Verbal - 31.
Was kind of expecting more here, cos I'm usually good at verbal. And while I was doing this section, I actually felt like I was doing well. Which is why the score surprised me even more. I was afraid I won't get to finish the section, but I actually had almost 7 minutes for the last 3 questions.
Incorrect questions:
CR: 6/11...really, really bad.
RC: 3/13...but I consider it pretty damn good. 2 reasons: firstly, I'm usually scared of RC cos of my slow reading speed. But I guess it isn't that slow, and what I read from PR really helped me. Secondly, the 3 questions I got wrong were from the same RC - cos I didn't GET it! Was a science passage, but got a lil too complicated to get while trying to speed read I guess.
SC: 5/17. That's over 70% accuracy. I think it's alright.

Quant - 44.
Man, this section really sucked. I was so bloody slow. I actually ended up randomly clicking options from question number 26, all the way to question number 32. I think in about a minute or so. Seriously, I was so slow. Even out of the 25 I did answer, I got only 15 right. That's terrible. I ended up guessing on some of those 25 too! Sheesh. I need to study so much more here. Need to do lots of practice questions. Do some of my CAT stuff from last year. Some topics I def need to cover - Geometry (co-ordinate plane!), AP/GP, number properties (can try doing it from that CAT aptitude book I have, or my sister's IMS BRM, or TIME material), time,speed&distance, averages! Once I'm thorough with different types of questions, I'll have to do OG and Kaplan questions under timed conditions. Tenaday might help in this. I got pretty confused in DS questions. Wow, basically, a lot to work on.

Tomorrow morning I'm not waking up early to study. And I'm meeting a friend for dinner to help him with his CAT verbal. Hopefully I can be of some real help!

Happy studying!

PS. Just posted on PagalGuy.com's thread...gives a short recap of what I've done till now, and about my areas of concern wrt first GMATPrep test. Find it here. ankurgupt was very sweet to post a quick reply to my queries, and you can find his post here. I'm definitely going to use his advice. Trying to get a hold on MGMAT CR Guide.


Day 14: MGMAT's Geometry Guide - Chapter 1 (Polygons)
Day 15: PR CR theory
Day 16: Revise RC notes from PR & give GMATPrep #1

A GMAT Prep software & Thomas Friedman revelation

From MBA.com:

"GMATPrep software features:

• A 15-question practice section for each type of GMAT question, with answers and explanations for each question
• 2 full-length computer adaptive practice tests with answers (detailed explanations of answers are not included) 
• Accurate computing of Verbal and Quantitative scores, which you can use to judge how prepared you are for the actual GMAT exam
• A comprehensive math review
• Real-time scoring"

Ummm...ok. I didn't know about points 1&4. My cousin gave me the CD for this software many weeks ago! I should go through this tonight, esp the comprehensive math review part! (Edit: Added this to the last post)

On a side note...Thomas Friedman is amongst my most favourite columnists of all time. I have been hooked to his writing since I was handed a worn down "Longitudes & Attitudes" a couple of years back. And today, I discovered his NY Times column on the net! I know, I know. Not such a great discovery. But it has made me very happy! Access to his writing! I love it!

Update/ Day 12 & 13

Firstly, I've updated the Important Links post with more useful sites and comments on the ones I've gone through.

I was supposed to be done with PR Math Bin 4 and making an error log by now. Done neither.

What I have done is:
(Day 12) 1. a few questions from PR Math Bin 4
(Day 13) 2. a few questions posted on a really cool BeatTheGmat thread: Problem Solving for 780+ aspirants. I realised there may be lots of geometry theorems and properties that I don't remember from last year CAT study (there were quite a few). So then i was confused about which resource to use as a comprehensive GMAT specific geometry review. Can't find one. People say use MGMAT's Geometry book, but not sure if it'll be worth Rs.1200. I guess I might have to do with knowing some extra geometry formulas. Will be looking up last year CAT notes.
3. a few questions and some theory (mainly probability and P&C) from PlatinumGMAT - it was definitely of some help.

But man, I'm really confused about what level of questions are asked at 700+ and 750+ levels. I don't mind going through my CAT Math books...but won't that be too much?!

I guess this mindset of wanting to know all the theory first - completely and thoroughly is taking me nowhere. And why I haven't done anything substantial for the last 1 week - I've been out every single night and coming back home really late. And I have to go out for dinner tonight AGAIN! Argh...and no, I can't escape it. Family dinner.

Things I should finish before Sunday morning (in the following order):
1. MGMAT Notes (mainly - Geo) (23rd Oct - TODAY! Edit: This should not take too much time, so I shouldn't worry about completing this before I go out for dinner tonight. Also go through GMATPrep's "comprehensive math review", esp the Geometry part!!! And add all the additional info to FCs)
2. PR CR theory (24th Oct morning)
3. Make error log
4. Put up questions (with solutions) that I've done (haphazardly) from BeatTheGmat, MGMAT, etc (FIGURE OUT WHERE U DID QUESTIONS FROM!!!) on this blog - make it my resource of all the questions I didn't know how to do (or make a notebook with all such "challenge questions")
5. Revise RC notes from PR

Sunday Morning : GMAT Prep (NEED to give this)

Plan for this week

So, Diwali's come and gone. And so have all my plans for studying. Not easy to do in the festive mood. Anyway, I finally pushed myself into completing PR Math Bin 3, and got 4-5 wrong out of 24 I think (will update with exact numbers later). That was Day 10. Have still not made an error log. Have still not taken Diagnostic. Still not done a single Practice GMAT under timed conditions. Wow, this is starting to really suck. 7 days of almost no solid GMAT prep. Yeesh! Anyway, we never lose hope. Here's the plan for the week...

Starting today...
20th, Tue - PR Bin 4 (5 qs) [Day 11]
21st, Wed - PR Bin 4 (10 qs)
(eve) make error log
22nd, Thu - PR Bin (left over qs)
(eve) error log (for morn qs)
23rd, Fri - CR from PR, few prac qs from Verbal Bin 2
(eve) 10 qs
24th, Sat - Verbal Bin 2 (complete)
(eve) Verbal Bin 3 (atleast 1/2) and error log update (if not done already)
25th, Sun - MGMAT free practice full-length timed test
(eve) analyze everything + make plan for next week

PS. At some point, might want to read up about AWA so that can answer MGMAT practice test with SOME clue!

Challenge Problem (CP) #1

From now on, I'll post the problems I find on the net that I find challenging, didn't get in the first try or didn't solve by the better method. Here's the first one!

NOTE: Whenever the problem is from MGMAT's CP of the Week, click on the link to go the original source of the problem.

MGMAT Challenge Problem of the Week


10/05/09

Question

Xander, Yolanda, and Zelda each have at least one hat. Zelda has more hats than Yolanda, who has more than Xander. Together, the total number of hats the three people have is 12. How many hats does Yolanda have?

(1) Zelda has no more than 5 hats more than Xander.

(2) The product of the numbers of hats that Xander, Yolanda, and Zelda have is less than 36.

Answer

Write x for the number of hats Xander has, y for the number of hats Yolanda has, and z for the number of hats Zelda has. From the question stem, we know that x < y < z and that x + y + z = 12. Moreover, since each person has at least one hat, and people can only have integer numbers of hats, we know that x, y, and z are all positive integers. With this number of constraints, we should go ahead and list scenarios that fit all the constraints. Start with x and y as low as possible, then adjust from there, keeping the order, keeping the sum at 12, and ensuring that no two integers are the same.

Scenario	x	y	z
(a)	1	2	9
(b)	1	3	8
(c)	1	4	7
(d)	1	5	6
(e)	2	3	7
(f)	2	4	6
(g)	3	4	5

These are the only seven scenarios that work. As a reminder, we are looking for the value of y. Now, we turn to the statements.

Statement (1): INSUFFICIENT. We are told that z – x is less than or equal to 5. This rules out scenarios (a) through (c), but the last four scenarios still work. Thus, y could be 3, 4, or 5.

Statement (2): INSUFFICIENT. We are told that xyz is less than 36. We work out this product for the seven scenarios:
(a) 18
(b) 24
(c) 28
(d) 30
(e) 42
(f) 48
(g) 60

We can rule out scenarios (e) through (g), but (a) through (d) still work. Thus, y could be 2, 3, 4, or 5.

Statements (1) and (2) together: SUFFICIENT. Only scenario (d) survives the constraints of the two statements. Thus, we know that y is 5.

The correct answer is (C): BOTH statements TOGETHER are sufficient to answer the question, but neither statement alone is sufficient.

Update/Day 9

Sorry for not updating earlier!

Day 6: MGMAT FCs - Word Translations (WT)
Day 7: MGMAT FCs - EIVs
Day 8: Theory (only formulas) for P&C, Interest (SI & CI), Sequences (AP,GP)
Day 9 (TODAY, 13th Oct): Just gave a 40 minute Math Diagnostic on MGMAT site. Was good! But questions were of 200-500 level. I got 19/20 questions right. The 1 I got wrong was silly - was a remainders question, and I should've just used common sense instead of trying to fit in a formula. Anyway, yay!

If I'm not too tired in the evening, I'll try doing some more from IMS BRM material on P&C...let's see.
Btw, I'm going to pay for GMAT by myself! :-) (earlier, my parents were going to)
I will be done with it by Dec end, and then...I'm going to apply to BCG, Bain & Co, and other consultancy firms in that league. I want to work there!!! I *will* work there.
GMAT studying, as you can see, is going at a slow pace, but it's consistent atleast. I want to try giving the OG11 diagnostic by this weekend (3-day weekend coming up! Yay Diwali!)

I'm off to try exercising a little before I go to office.

Happy studying!

Day 4 & 5

I didn't write because I had been unable to cross off things from my 'to do list' on time. Anyway, I am done now.
1. Word Problems theory from OG11
2. Make FCs for Word Problems


Day 6 to do:
MGMAT FCs - EIVs.

Pending:
Read Interest (CI & SI) from Career Launcher book.
Redo Time, Speed & Distance basics from TIME (in-class) notes last year.
P&C - class XII.

Day 3

Things to do:
1. OG11 Geometry review - read & make FCs.
2. MGMAT Geometry FCs.

That means I'm done with all the items on my Things To Do list for the day!!!

Add new concepts from MGMAT FCs to own FCs.

Day 2

Yesterday, I finished MGMAT FCs - Number Properties (NP).

Today:
1. Made FCs (flashcards) for OG11 Arithmetic section (not completed fully; permutation & combination - may need to use class XII books and tuition notes)
2. Went through MGMAT FCs FDPs(Fractions, Decimals & Percents)

On Saturday (10th Oct) I plan on giving the MGMAT Free Basic Math Diagnostic (find it here). You will need to register with MGMAT website for it.

Hope that your studying is going well!

Back after post Warm-up Test depression phase / Day 1

What I've done today (till 1:41 pm):
1. Some MGMAT flashcards: Number Properties - pretty basic till now
2. Read the 1st chapter of MGMAT SC Guide (the previous edition).

Related studying to be done:
1. Will try completing the rest in NP set in the car on my way back home today
2. Solve questions from the guide itself (considering solving OG11 qs mentioned in book as well)

Another addition to Math review is http://www.gmattutor.com/basics.html which includes a worksheet for math formulas or "things to remember"

PS. Today is a Monday. The beginning of a brand new week. The dawn of renewed enthusiasm for cracking the GMAT *whiplash*! Therefore, this is Day 1. And the countdown to GMAT on December 15th, 2009 begins.

Ack!

Just found this on a website:
MGMAT CR and MGMAT SC come without any practice questions. Instead they refer to questions in the Official Guide 12, so you must buy that book to practice and preferably should not have covered it in the past. On the positive note - all Manhattan books come with access to 6 online CAT tests, so you should buy at least one Manhattan GMAT book (any one of them).

Must change my study plan a bit!

A little behind / Study Schedule - the big picture

Sigh...

So yes, I have been horrible. I didn't study yesterday (friend's birthday), and today being a holiday, I've been out all morning, and been glued to the television since. And I'm going to leave soon to meet my niece and nephew! They're too cute! :-)

Of course, I'll still study a certain amount today. Which is why I'm writing to update you on how my GMAT prep is coming along.

Firstly, I read about a GMAT experience which made me think my original plan was pretty good. So, this is the revised study plan:

1. Learn the concepts well from PR (done), OG11, MGMAT notes, Platinum GMAT website (links in previous post). After every topic, practice a couple of questions (untimed) for each. Initially I didn't know where to find these practice questions from. Then I realized that the MGMAT flashcards are perfect for this! You'll have to see them to understand why. I'll also do PR Bin questions & 1/4th of OG11.

2. Give diagnostic test from OG. This will help me find my weaknesses to work specifically on them.

3. Review or add more concepts to #1, and then do another 1/2 of OG11, effectively finishing 3/4th of it.

4. Give a practice test (either GMAT Prep or MGMAT?) Analyse the test.

5. Do TIMED questions now, in maybe the following order:

- 1/4 of OG 11 left.

- Kaplan Premier.

- OG12.

- Kaplan Advanced.

- Questions from other resources.

- OG 12 again.

Note: Intersperse MGMAT, Kaplan, GMAT Club diagnostic, GMATPrep other free tests whenever you feel you have learnt enough new things or learned from ur mistakes. Pick up MGMAT SC, or other concept building books as & when you feel the need to.

What I'm done with: So, I've started reading OG11 for more concept building (done with PR sometime in mid-September). Only the Word Problems section remains. But, I still need to make flashcards from my OG11 reading. And also practice from MGMAT flashcards. Will try catching up by tomorrow!

Happy studying till then!

PS. I've updated the links in the previous post, and may continue doing so over the course of my preparation. I had, however, considered myself to be ultimately cool for being the first person to ever do this. But, BeatTheGMAT beat me to it. Their list is more extensive, but does not include ALL the links I've mentioned here (like how to do practice problems, analyzing your test and mental math practice). Mine is a more personalized list of what I like and find relevant :-)

Edit: For those of you who want to look at other study plans, GMAT Club has their own here.