Please guide

[velchal_rao]

Hello,

I have written my GMAT recently .It was a big disaster .
I figured i have to improve my timing issue and also improve my
accuracy in calculations for simple problems .

Someone told if i do mental math i could improve my calculations .
Is it right ?

Please suggest ways i can fix my timing issues .

I have started analyzing problems as mentioned in the posts .
But this analysis is taking time for me and also sometimes it so happens even after doing this I am unable to identify a new problem
based on same topic ...where i am going wrong ?

why am i not able to figure it out within time ? why am i not able to get the idea sometimes that it belongs to the same concept ?
Is my analysis really going in the right direction?

Few examples of my analysis :
I.
Find the Sum of all four digit numbers formed using the digits 2,3,4 and 5 without repetition?

Topic :
Digits , Probability and logic

Here its asking sum of all four digits formed from 4 digits but if the problem asks sum of 5 digits from 4 digts and adding some other conditions like should be even or odd and other way with repetition and without repetition

-How would you solve it with in two minutes ? in 2 min?

-How would you make sure you remember this approach in the future ?
-Are there any shortcuts I can remember ?
-Do you immediately recall any problems similar with above one ? Yes ..........How many four digit numbers ...? Or What is the sum ?

The formula is : (n-1)! (Sum of digits ) (1111...n times ) (n-1)! (Sumof n digits ) (111....n times )
Without repetition

Solution:
3! (2+3+4+ 5) * 1111

Is there any other better solution than the above ?
...............................................................................................

II
2.
Machine x and y produced identical bottles at different rate s .Machine X, operting alone for 4 hours , filled a part of a production lot ; then Machine y , operating alone for 3 hours , filled the rest of the lot.How many hours would it take
Machine X operating alone to fill the entire production lot ?

1. Machine X produced 30 bottles per minute

2. Machine X produced twice as many bottles in 4 hours as Machine Y produced in 3 hours

a.
What are the problems I faced trying to solve this problem -Translating of words
b.
What are the concepts involved here ?topics?
Ratio + Wok done
c.
What is work done ?
-Number of bottles produced - dint get this at first instant

d.
How are ratio and work related and how is this info helpful in solving the problem ?

-Looking at Statement 2 we can say machine X filled 2/3rd of lot in 4 hours so total work or 1 can be done in how many hours ?

2/3 - 4 hrs
1 - ?
e.
Can you solve it by Factorizing or PIN or RTD format or Equation ?
f.
How would you write the above info in Equation format ?
4x + 3y = Job done
4x = 2 * 3y
Number of bottles per minute * number of minutes = Number of bottles produced
Is there any other way to solve this problem ?
need to try;
Best way to solve within 2 minutes is :Equation and Ratio

g.
Where would I see someone falling in to trap for these problems ?
-First not understanding , next not knowing how the equation should be written or how to know that information given in ratio in terms of work done will help solve the problem

.........
h. Are there any other simlar problems I can think of ?

h.1. Machines X and Y simultaneously at their respective constant rates .If machine X produces 400 bolts perhour , how many bolts do machines X and Y produce per hour ?

1. Machine X takes twice as long to produce 400 bolts as as it does for machine X and Y , Working together , to produce the same number of bolts
2. Machines X and Y produce bolts at the same rate


h.2. Working together , John and Jack can type 20 pages in one hour . If they would be bale to type 22 pages in one hour provided Jack increased his speed by 25%,
What is the ratio of Jacks normal typing speed to that of Johns ?
a. 1/3 b. 2/5 c. 1/2 d. 2/3 e. 3/5 Note : The answer choices are simple enough that PIN should work
The other method : Use RTD format / Equations

Solution:
RTD format/ Equations
(x+y)*1 = 20
(x+ 1.25y) = 22
.................................................................................................

III. Customization of problems 5.a. A certain game , a large bag is filled with blue , green and red chips worth 1,5,x and 11 points each respectively .The purple chips are worth moer than green chips but less than red chips .A certain number of chips are selected from the bag .If the product of the point values of the selected chips is 88,000, how many purple chips were selected ?

Analysis for 5.a -What are the topics ?
Factorization , primes and its powers

-What is the operation ?
Product , well this is the best way for factorization anyway .

-what kind of number logic is implemented ? "Unscramble " 2^6 = 4^3 = 8^2 = 64^1 , the problem hides that its using this info to get to the correct answer

-Where could someone fall in trap ? By reading the question , the student could think it’s a probability Q or combinatorics without knowing its testing simple concept
-How would I rephrase the Question ?
What is the value of n in 2^n = 4^n = 8^n = 64^n



5.b. For any integer k > 1, the term " Length of an integer " refers to the number of positive prime factors , not necessarily distinct whose product is equal to k . For example, if k = 24 the length of k is equla to 4.since 24 = 2 *2 *2 *3 . If x and y are positive integers such that x >1 ,y > 1 and 3y + x < 1000 , what is the maximum possible length of x and length of y ?
.............................................................................................


IV.
6.If y(u-c ) = 0 and j(u-k) = 0 , which of the following must be true , assuming c < k ?
a. yj <0 b. yj = 0 c.y=0 d.yj>0 e. j=0

1.How is this problem made difficult : using all variables .
2.How can I make it simple ? By using numbers in place of variables ?

3.Do I do it algebraically or PIN ...... doing these kind of problems -algebraically is screwing your self in test , the better approach is --PIN a is not always the best option,
here its an exception because "ALGEBRA WORKS BETTER HERE "
4.But the whole problem is about what kind of numbers do I choose so that I can solve this problem in 1 minute NOT WASTING TIME

5.What is the problem testing here ?
Its testing the "POSITIVE AND NEGATIVE properties of numbers disguised in INEQUALITIES and EQUATIONS AND 0 PROPERTIES disguised in INEQUAIiTIES and Equations
6.Why would someone fall in to trap ?
a. choosing wrong PIN values
b. forgetting the condition given in problem
c. finding the wrong value or forgetting what the q is abt and answering something else
d. solving inequalties and equations the wrong way
j(u-k) = 0 ; ju = jk ... so what ? wrong

RH.S sides both are equal so , you equate y(u-c) = j (u -k) wrong


Point to be noted : I SEE
> 0 , < 0 , = 0

I THINK/I DO
The problem is giving info in equations and inequalities but its really testing
positive , negative and 0 properties of numbers

7.How would a problem appear using the same principals in a different way ?

a.The operation could be changed from multiplication to division or something else
b.The could be one variable in fraction format or using a quadratic format
c.Fraction format u generally use different PIN VALUES to test
d.Value based q or Yes or no q

e. EXAMPLES :
1.X(X-5)(X-2) = 0 x=0 or x =5 or x = -2
2.Find the vaue of XY / Z OR XYZ given some conditions
3.x^2 = 2x - 1 this is nothing but (x -1)^2
4.1/x , x^2, x given some conditions
5.x, y^2 , z^3

or the Q could be : Is x^2 y^3 z^2 >0 ? >0

1. xy > 0 2. yz<0





Please help .Thank you very much .

[StaceyKoprince]

I'm sorry that you had a disappointing experience on test day.

I'll be able to advise you better if you can provide me with additional information about your strengths and weaknesses. Use the below to analyze your most recent MGMAT CAT (this should take you a minimum of 1 hour):
https://www.manhattangmat.com/blog/inde ... ts-part-1/

Also, read these two articles:
https://www.manhattangmat.com/blog/inde ... lly-tests/
http://www.manhattangmat.com/blog/index ... -the-gmat/

Figure out your strengths and weaknesses as well as what you think you should do based on all of that. Then come back here and tell us; we'll tell you whether we agree and advise you further. (Note: do share an analysis with us, not just the raw data. Part of getting better is developing your ability to analyze your results - figure out what they mean and what you think you should do about them!)

For your specific questions:
1. (find the sum...)
This is not a GMAT-format problem. I can't tell you exactly how I would do this on the GMAT, because this is only "half" of a GMAT problem (there are no answer choices, if PS, or no statements, if DS).

Let's assume that it's PS and you gave me 5 answer choices. I'd first look to see what the answers are like, since that influences my solution process. For example, if the 5 answers all have different units digits, then I know I can just find the units digit of the sum and save myself a lot of time. Alternatively, if the answers are spread far apart, then I might just be able to estimate an overall number and then pick the answer closest to that number.

I guarantee you one thing: a problem like this one will never actually require you to calculate the exact number. They're not trying to see whether you can do a bunch of math in your head (or even on paper) - you will actually have access to calculators and computers in the real world, and you're not applying for some kind of math degree.

If you do want to take more about how to solve that specific problem (the full problem - with answers or statements), then feel free to post it in the appropriate Quant folder.

#2. This one is also not GMAT-like. (The GMAT will always specify that the machines operate at their respective constant rates, for example. If you don't actually say this on data sufficiency, then the answer would always be E.)

So that leads me to my next question: where are you getting these problems? Part of the issue might be that you're not studying relevant problems.

You are asking yourself good questions in your analysis - but I want to make sure that you're actually studying from good problems as well.

#3. The one about the chips was written by someone who was probably looking at a real OG problem: OG13 #219. I'd study the real problem.

The one about the "length" is almost identical to an official guide problem. The answers are missing and the question is not asking quite the same thing.

So, I'm going to stop here. Issue number 1 is that you're not studying from official problems. Most of these problems are lacking in some serious way that will cause you to prioritize the wrong things in your study. For example, I wouldn't even consider solving a PS problem without first glancing at the answers to see how that might affect my solution process. If you're studying PS-type problems that don't have answer choices, then you're studying for a math test, not the GMAT. The GMAT is not a math test (not in the traditional sense).

Read the articles that I linked earlier in this post - the ones about what this test is really about and how to study. Analyze your most recent MGMAT test results. Then come back here and tell me what you discover.

[velchal_rao]

Thank you very much for the response and time . I know my post was confusing and long. I will take your advise and work on official guide. I will come back with my CAT exam analysis with complete examples.

Regards,
Sameera

[StaceyKoprince]

Sounds good - good luck!