Veritas Prep PS Forum Expert - Karishma - Ask Me Anything about Math

How about the case when A sits next to C but not to B. A does NOT refuse to sit beside C unless B sits next to him on the other side. We can have AC sitting together in 2 ways, one of the other 5 (except B) sitting next to A on the other side and the other 5 people arranged in 5! ways.

This can be done in 2*5*5! = 10*5! ways

ok Karishma I have read your posts and found out that you are better at understanding the internal working of mathematics (QUANT) in connection with GMAT then anybody else in this forum. The problem with me is that this is my first ever CAT test in life so I went head on brute force with GMAT which is to "know all to solve all" but I think GMAT is ocean and this strategy is taking me nowhere. I have gone thru all the basic quant requirement from reputable resources and my concepts are fine.

so here is the problem i gave the GMAT club test and scored 8/31 correct and wrote a furious review about the club test but later when I reviewed where I went wrong I figured out that, it is not the theory where I am missing the problem is something else.

I want to give you an analogy to understand what that is. Suppose an amateur starts to play chess what he will see is the pieces and how to move them but he will not know all the tactics. Maybe he will even lose the sight of pieces where they are placed amid game due to extreme concentration on some other part of the board. But it does not mean that his brain is dull it means that his brain is still not wired for that. what does wired means here is that he can not spot the common patterns quickly, yet.

The problem what I am facing is I am doing well in 600-700 level range but when it comes to 700+ I think I am not wired and I think one cannot be wired for the 700+ since each question is a stand-alone question and requires some cognitive thinking which takes time. Maybe after going through 100s of 700+, I could say there is a pattern too but for time being I have to stand at 700+ and invest some brain there to find the pattern which costs time in the actual test. I don't have time to go thru 100s of 700+ to wire my brain so what I have decided is I want Q49 for which best range to practice questions is 600-700.

I have gone thru all OG tags 600-700 here is where I want your help I want you to spot me what type of question bank I should practice to know all common pattern in Q49 range so that I don't have to lose time in making the mental picture and doing the cognitive thinking.

Side note.
I am not running away from nor I am afraid of 700+ given more time I could crack them easily but I am being smart here by saving time, rather than getting the punch on the face and learn from it "I want to float like a butterfly and sting like a bee".

Ah! The first query on my thread is a challenge!
What I get from your post is that you are looking to cover all patterns (or at least as many as you can) of medium-difficult level. For that, OG doesn't really give an accurate picture. GMAT Official practice exams will do a much better job (though not exhaustive). Also, standard test prep companies take care of introducing most patterns over their coursework.

But if I am to be honest, I don't really believe in "questions are made keeping a finite number of patterns in mind" theory. I believe in concepts. After that, give me a question of any new pattern and I will solve it. 700+ level question are harder only because it is more difficult to recognise the concept being tested in them. Application of the same may not be troublesome at all.

Karishma-Thank you for taking the time out to answering questions. I have been your follower of your solutions since many years and must say you are a star when it comes to GMAT. So here are my questions.

1. Can you share inputs on how to get to V44+ from V35/36?
2. How do I move from Q47/48 to Q51?
3. How do I get to 90-100% accuracy both in verbal and quant?

Also, I am guessing you would be having a high score to your credit?

Thanks.

Here is the thing about DS questions - people love to solve them by plugging in numbers and I think that strategy often backfires. Until and unless one is super fast in one's calculations and has an intuitive understanding of number properties and how the behaviour of numbers changes at each transition point, one should not use number plugging. But then, if one does have all those skills, number plugging is not required. Hence, all in all, in my opinion, it is a lose-lose proposition.
I am not saying that number plugging is useless:
- I agree that for easier questions, number plugging could work (though it might take more time than the more logical approach).
- Also, for harder questions, it can help you understand the problem and figure out the logic/pattern.
- It also helps you weed out special cases such as n = 0.
But the dependence we often have on this approach since it seems easy to follow is unwarranted.

Focus on the logic being tested in a question and the issue of "being overcautious" or "missing something" will not arise. Send me some links of functions and inequalities questions that gave you a hard time and I will tell you what I am talking about.

Solution:

P(A) = .5
P(B) = .4

You need to find P(Neither will happen). Think about the corresponding sets concept. Neither is given by Total - n(A or B)

P(Neither will happen) = 1 - P(A or B) = 1 - [ P(A) + P(B) - P(A)*P(B) ]

We don't know the relation between the events A and B so we don't know what P(A and B) is. Try to think of this in terms of the venn diagram.

To minimise neither, we need to maximise P(A or B). So A and B should have minimum overlap.
Assuming A and B are mutually exclusive events, P(A and B) = 0
P(Neither will happen) = 1 - [ P(A) + P(B) - P(A and B)] = 1 - [.5 + .4 - 0] = 0.1

To maximise neither, we need to minimise P(A or B). So A and B should have maximum overlap.
Assuming B is a subset of A , P(A and B) = 0.4
P(Neither will happen) = 1 - [ P(A) + P(B) - P(A and B)] = 1 - [.5 + .4 - .4] = 0.5

Answer (A)

Usually, in actual application based GMAT questions, you will not be required to do such calculations. Sometimes, the lower level questions might have a direct calculation such as this one in which approximation would work just fine. It will be a rare question in which you actually need an exact value of this.

To approximate: \(0.17 * \frac{26.4}{1.65} = 1.7 * \frac{2.64}{1.65}\)

Double of 1.65 is a bit more than 3 so 2.64 is about 1.5 times of 1.65.

So we get 1.7 * 1.5

1.7 is a bit less than 2 so our answer will be a bit less than double of 1.5 i.e. a bit less than 3.

If you do the actual calculation you get 2.72 so you are close.

I prefer to stick to smaller numbers rather than make them larger. That is why instead of changing 26.4 to 264, I changed 26.4 to 2.64.

That said, if you do need exact values, remove the decimals to get 17*264/1650.
Looking at even numbers, my first instinct is to divide them by the highest power of 2 i.e. is it divisible by 2 or 4 or 8...
The next obvious common factors are 5/3 then 11 etc...

You can find everything in below two topics:

Check below:
ALL YOU NEED FOR QUANT ! ! !
Ultimate GMAT Quantitative Megathread

Hey Montyyy95:

"for every consumer that likes only product B, 3 also like product A"

means for every 1 consumer that liked ONLY B, there are 3 consumers that liked A 'ALSO' which means that these 3 liked B as well as A.
This means ratio of
(ONLY B) : (B and A) = 1 : 3

Hope this clarifies! Let me know.

Hey nikitamaheshwari:

Please check my signature below.

Hey aashigarg,
Here you go:
https://gmatclub.com/forum/the-average- ... l#p2699237

I solve these questions using the concept of deviations since it makes the numbers easy to handle.
Alternatively, you can use the weighted formula for 3 like this:

Cavg = ( C1*w1 + C2*w2 + C3*w3)/(w1 + w2 + w3)

20 = (25*5 + 16*4 + C3*6)/15

You get C3 = 18.5

ravish844:

When we are given "if silver is twice as heavy as aluminium" it means that for the same volume, silver is twice as heavy as aluminium.
So if we take V volume of aluminium and V volume of silver, if weight of this much aluminium is W, weight of the same volume of silver will be 2W.

This means that if we have V volume of aluminium, and we have V/2 volume of silver, weight of both will be W.

This is what the question tells us about the first coin: "the volume of aluminium in the alloy is twice that of silver"
So we realise that weight of both in the coin is the same. Since weight of coin is 30 gm, weight of both is 15 gm each.

Yes, if the volume of Aluminium in coin 1 is V and it weighs 15 gm, volume 3V of aluminium in coin 2 will weight 45 gm.

A greater number of newspapers are sold in Town S than in Town T. Therefore, the citizens of Town S are better informed about major world events than are the citizens of Town T.

Each of the following, if true, weakens the conclusion above EXCEPT:


(A) Town S has a larger population than Town T.

(B) Most citizens of Town T work in Town S and buy their newspapers there.

(C) The average citizen of Town S spends less time reading newspapers than does the average citizen of Town T.

(D) A weekly newspaper restricted to the coverage of local events is published in Town S.

(E) The average newsstand price of newspapers sold in Town S is lower than the average price of newspapers sold in Town T.

The units need to match.

Rate = 5 lines/ 20 sec
Time = 14 hrs = 14*60*60 sec

\(Work = \frac{5 lines}{20 secs} * 14*60*60 secs = 12600 lines\)

Staphyk,

You can put my name in the author field of the Advanced Search feature of GC and search for all my posts in whichever forum you wish to:
https://gmatclub.com/forum/advanced-search/

Different word problems require different approaches. I do favour going one line at a time and evaluating each till I reach the question stem. Here are some recent solutions:
https://gmatclub.com/forum/of-the-stude ... l#p2182147
https://gmatclub.com/forum/in-order-to- ... l#p2182154

Sometimes, you will need to consider the entire question to form equations:
https://gmatclub.com/forum/veritas-prep ... l#p2182196

Yes, this can be a source of confusion. That is why we have a post on it on our blog here: https://anaprep.com/algebra-squares-and-square-roots/

It discusses the cases you have brought up and the 'why' behind each. Let me know if you still have doubts.
Now that you are familiar with principal square root concept.

\(\sqrt{X^2} = |X|\)

\(\sqrt{X^2}\) is the principal square root of X^2. So whatever you get after finding square root, it will be positive. But what if X is negative? To ensure that you still get a positive value, you take |X|. Let's look at an example.

\(\sqrt{5^2} = \sqrt{25} = |5| = 5\)
This is fine. What we get is a positive number. Since we are talking about principal square root, this is what is expected.

\(\sqrt{(-5)^2} = \sqrt{25}\)
Now what is the answer? It is still 5, right? Still the principal square root. But if I say that \(\sqrt{X^2} = X\), that gives me -5 as answer because X = -5.
But the principal square root cannot be negative.
So I say \(\sqrt{X^2} = |X|\)

\(p^2 = (q+1)^2\)
All you can say in this case is that their absolute values are the same.
|p| = |q + 1|

Why?
Taking square root both sides, you get
\(\sqrt{p^2} = \sqrt{(q+1)^2}\)
\(|p| = |q + 1|\)

The 5% and 10% increase is on the initial number of R voters and S voters.
wR/wS = (5 - 8)/(8 - 10) = 3/2

The initial numbers increased by 10% and 5%.
So new ratio became [3*(11/10)] / [2*(21/20)]
The new R/S = 3.3/2.1 = 11/7

Fraction of voters who voted R = 11/(11+7) = 11/18