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How to improve your QA percentile – Part III

In the previous two posts, we took a look at the first two building blocks to increase your score and percentile on CAT Quant — Accuracy & Question Selection. In this post, we will look at the third building block — Speed.

Increasing your speed by at least 2x is a function of changing three things in the way you execute a solution:

  • increasing your number-crunching muscle
  • reducing your dependence on writing extensively
  • viewing problems through an alternative lens

Increase your number-crunching muscle

Find (1² + 3² + 4² + 5² + 7² + 8² + 9² + 11² + 12² + 13² + 15² + 16² +…….49²) / 1249  if it is an integer.  (TITA)

This is a question from a SimCAT and most people would have let the question go. Upon reading the solution, they would have become doubly sure that it was a good leave.

But as we have often seen in T20 cricket, guys with huge reach and immense power can send balls, which can be potential dot balls to other batsmen, sailing into the crowd.

I decided to take on the above problem using some number-crunching muscle

Firstly, I knew that this numerator was the sum of the first 49 squares minus the even squares— we just need to substitute n = 49 in the formula, n(n+1)(2n+1) /6 and minus the sum of the missing squares.

49*50*99/6 can be reduced to 49*25*33 which can be approximated to be 50*25*33 = 1250*33 = 12*3 = 36 so a value greater than 36000, also this has to end in a 5 since it is 49*25*33.

If I ignore the values that need to be subtracted — the even squares — and look at the denominator 1249, I know the answer has to be 35 since the value is greater than 36000 and has to end in a 5, 1249 has to be multiplied by a number ending in 5 to get a value ending in 5.

But the catch is that some values are missing from the sum of squares, which I promptly listed:

2² + 6² + 10² + 14² + 18² + 22² + 26² + 30² + 34² + 38² + 42² + 46²

We can quickly estimate the last digit of the sum of these terms — 4,6,0,6,4,4,6,0,6,4,4,6 — 0, so even after subtracting the value has to end in 5 and hence the answer has to end in 5, so if without subtracting it is 35, then after subtracting it has to be 25, 15 or 5.

I set about quickly estimating the value of the above terms by starting from the right end since the squares of the larger number will make up most of the value and the smaller ones can be effectively ignored.

I am writing the approximation as I processed it mentally:

  • 42² + 46² = Two 40s, more than 1600, 1600, so around 3500
  • 30² + 34² + 38² = Three 30s = more than 1000, 1000, 1000 = around 3500
  • 22² + 26² = 400, 600 = more than 1000
  • 2² + 6² + 10² + 14² + 18² = less than 1000

So from a value greater than 36000 I need to subtract around 10000 so it will be around 26000 and hence value greater than 26000 ending in 5 when divided by 1249, to give an integer, has to yield 25 since 12*2 = 24 and 12*3 = 36

Thinking is always faster than writing so the actual time that I took for this crunching process was under 2 minutes.

Given that the CAT is a test of speed, what matters is not knowing how to solve but how quickly you can reach from knowing how to solve to the final answer.

This can only happen if you have some serious number-crunching muscle — extensive conceptual clarity cannot compensate for this muscle. You need to ask your self

  • when the clock is ticking and you are executing a solution, can you break the numbers down or will you buckle under their load?

If your answer is sometimes I can crack, sometimes I buckle or most often I buckle, then you are not yet in shape to take the CAT. But you have three months to build some serious muscle by memorizing all of these:

  • all squares from 2 to 30
  • all cubes from 2 to 12
  • all powers of 2 from 1 to 12
  • all powers of 3 from 1 to 6
  • all fraction and equivalent percentages from 1/2 to 1/11
  • tables from 2*10 to 20*10

Most of you want to do an MBA so that you can do high-quality, high-paying work. If that is the case then you should approach the 180 minutes of the CAT in a such a way that we do only quality work during the 180 minutes of the test.

  • Do you want to be calculating 29², if it is the answer to a TITA question?
  • Do you want to be calculating the value of 2 raised to 8 by starting with 2 raised to 5 in the middle of a problem?

All of these values should already be fed into and so deeply embedded in the system, that there is no gap between retrieving and executing the solution.

In short, you need to be the calculating-equivalent of a T20 big-hitting beast.


Reduce your dependence on writing extensively

A few years back a student came to have a chat with me, he was retaking the CAT and needed a plan. He said he was really good at Math but could not solve more than 22 problems on CAT 2016, which as you know had an easy and hence high-scoring QA. He was working with a good Consulting firm, had a good profile and was thus looking at premier schools that needed high percentiles.

My first instinct was to give him a piece of paper and a problem just to watch how he solved it. He wrote down around 10 steps on the paper and solved the problem and that was the exact reason why he was only able to attempt 22 questions.

Writing and executing the entire solution of a problem is the biggest speed-breaker or decelerator in front of you. Each one of you will have varying degrees of dependence on writing. Sometimes, the more diligent the aspirant, the more steps he or she will write (systematically and without clutter) while solving a question.

The problem is that this method will result in fewer than 15 attempts in 60 minutes and when coupled with a few mistakes will end up in a percentile that is perennially hovering in the 85 range.

So if you are among those who write diligently then you need to drastically change your approach to increase your percentiles and understand than

  • you are used to writing because you are used to submitting homework
  • you are used to writing because missing steps can mean fewer marks being awarded
  • you are used to writing neatly because so far good, clutter-free writing fetched you higher marks

None of the things listed above applies to CAT Math — just like none of the rules of Test cricket applies to T20 Cricket — no marks for handwriting, no marks for steps

How do you decrease the amount of writing you do? Start with the following steps

  • do not duplicate information from the screen on to your rough sheet
    • a man does a piece of work in 20 days, then do not write 20 or t = 20 on your paper, you are just executing robot-like steps without getting any closer to solving the problem
  • do not write what you need to execute
    • if you need to calculate the average of five numbers then there is no way you are writing 5 numbers with plus sign between them, drawing a line underneath them and writing a five; you need to just get adding and dividing without writing anything
  • start to skip writing down each step by executing intermediate steps mentally
    • if you have to solve 1/(x+1)  + 1/(x+2) = 2, then maybe the next step you should write is 2x + 3 = 2x² + 6x + 4

In short, write only if you cannot process the information in your head!

This is a question in one of this year’s SimCATs that I solved purely mentally when an aspirant who is working with us in the content team came to me and asked me to solve a  paper live to see how I approach a section to learn selection and speed.

The function F is defined as F(k) = 2k³ – 3k² – 5k + 7 and the function G is defined as G(k) = 2k³ + 1k² + 7k + 15. Find the product of all values of ‘k’ for which F(k) and G(k) are equal.

I knew that I had to equate the two since that is when they will become equal, the cubes cancel themselves out and if I take the remaining terms to one side, it becomes a quadratic with 4,12, and 8, which gets reduced to 1,3, and, 2, whose roots will be 1 and 2, making their product 2. This took about 60 seconds or fewer mentally.

Even if you take more time, the key is that there is no need to write. Some of you might say that if I do it this way, I’ll be making mistakes, it is like saying if I drive faster I will crash, but then you won’t win the race — it is about driving the fastest you can without crashing.

This is easier said than done since we have been conditioned over the years to equate writing with thinking and solving, so like the legendary dog of Pavlov, we start writing the moment we start reading a problem.

To practice the above steps consciously you should try a few special practice sessions.

  • Take a section test or an area test or the Quant section of a take-home SimCAT with your hands folded or your palms locked in front of you.
  • Have a pen and paper handy on the table to write only if the need arises
  • Force yourself to execute a few steps mentally
  • Do not be bothered about time running out, do not be bothered about the score

If you do not try out these things during practice you will keep doing the same thing over and over again and keep expecting different results, which alas is a non-sequitur (CR enthusiasts should check what this means).


Viewing problems through an alternate lens

The above heading might seem as if there is a standard lens and there is an alternate lens. In fact, nothing could be farther from the truth. What always matters is the most optimal solution to a problem. Why do we not find the optimal solution?

Reject the formula-first approach

Our gut reaction to solving a problem is to try to immediately fit it to a formula. In fact, when faced with a question we immediately ask ourselves — what formula do I know that can help me solve this.

A formula is only one of the tools that you will use to reach the solution that you have devised; they are similar to a surgeon’s or a mechanic’s tools. A surgeon does not decide on the kind of surgery to be done based on the tools he has, neither does mechanic decide on how he is going to fix a vehicle based on the tool he has!

So do not make formula-fitting your first step.

Do not algebraify a problem by force

If we do not go to a formula, we then start taking the first thing we encounter as X and we try to form an equation.

We feel that if we can convert English into Algebra, we have done our job but Algebra is just another language like English. What you have to convert it into is a logical language, which can still be in English but uses words or Algebra that uses symbols.

Do not convert all problems into Algebra, especially the Arithmetic ones.

Move to the question first approach

Put the question and what is finally asked as the first and most important thing. Work backwards from there to determine what you really need instead of trying to build towards the answer from the first bits of information. Information is never given sequentially and usually, the most important piece of information is given right at the end and that might make your whole job easier.

Do not treat the given information passively

On most good questions, the given information itself holds more than meets the eye, provided you are willing to at least turn it over in your palm to see a small latch that you can pull.

If you take it just the way it is and do not try to even squeeze a wee bit or cut it, a lemon is as good or bad as a stone or softball (in fact not even as good as those).

The methods we know of are a function of the teachers we have had

We are more or less a function of what we have been taught and made to do; there are always a  few who can see things by themselves but there are a great many who can do much better than what they if someone points the way.

How many really high-quality teachers have we had (and I do not mean by good because of their nature; I will prefer a horrible person who teaches stuff with fresh eyes to a good human being who teaches stuff in the most mundane of ways; there a few who combine the best qualities of the two types and I have had the pleasure of knowing two of them) ?

I started looking at problems differently after I encountered my colleague pulling off some amazing solutions (go through all of them); it did not feel like it was way above my league since it was more a question of approach and attitude rather than some genius intuition (which he does have) because it was something that was easily understood.

I figured that it was more about my ability to let go of my conditioned responses and less about my ability to find alternate solutions.

And surely enough over a short period of time looking for the fastest route to goal by looking at questions through an alternate lens became second nature to me as well.

With Quant, it was almost like it was with cricket for me. I have never thought of myself as a natural sportsman (like I never thought of myself as a natural QA guy) and got by with grit and competitiveness. So while I opened the batting for my department team, it was more a function of my ability to stay at the crease and maximise whatever I could with my limited but effective range of strokes I had at my disposal and the limited talent in our department rather than high-quality skill.

We managed to play almost everyday (back in the day we had annual exams so we could afford to chill all year and study at the end) and it is only at the end of three years and that too during a practice session that I stepped out of my crease and tonked the bowler (a gentle medium pacer) over his head for six. It had taken me close to 10 years of playing cricket to do it (and I can still step back into that feeling).

To find a new road, you have to first get off the old one, you need to step out of the crease as well during practice.

 

 

 

 

 

 

 

 

 

27 Comments

  1. Praveen Singh says

    Hello Sir, last 3 posts regarding QA enhancement has been very helpful and give many new perspectives and ways. Sir, I have a request. Please give same thorough analysis and strategies to enhance in VA-RC.

    Like

  2. Arnav says

    Hello sir, I have converted TISS, MUMBAI HRM. I want to know about the scope of HRM and its future potential.
    Also please shed some light on the career growth as to where one can see oneself after 10 years down the line as an HR. I have heard top IIMs folks usually are make 60-70L+ salary after 10 years experience. Few even more than a crore. What can I expect from TISS HRM?
    (wrt career and monetary terms)
    Also, will TISS help me to get into the top IT/Ecommerce companies like Google, Microsoft, Amex, Filpkart or top consulting companies in HR domain through campus placement or with few years work ex in HR?

    Like

  3. Rishi says

    Hi Sir,

    Sometimes back, you share the list of the books relevant to all the management-specific fields. Can you please share the link of the same here as I cannot locate it on the website?

    Like

  4. Jay Patel says

    Sir,I am unable to attempt more than 8 question in QA even if I am gone through most of the concepts except P&C and probability. and I don’t know what’s going wrong and ya,I know my speed and accuracy is very low.Can you please give me some solution?

    Like

    • Hi Jay,

      Hope you went through Parts I & Part-II of this post.

      The first task for you is to improve your accuracy that you have to do using the methods I outlined in Part-I. Any accuracy below 80% means that the time your spent is getting wasted.

      The next step is to use the methods outlined in Part-II to select the easy and moderate questions first. Start with the simple task of selecitng and solving only 12 questions and then slowly set higher targets.

      Another possible reason might be that while you learnt concepts you have not practised enough questions across areas for you be able to solve problems. This might also be the reason for low speed.

      Hope this helps,

      All the best!

      Like

  5. Tharun Srivathsa says

    Hi Sir! Thanks a lot for the three blogs on QA, it has helped me to increase my attempts and accuracy drastically.
    I have a small query,I am in my final year of BE ,I have scored 90+ in Xth, 85+ in XII and UG. I have done a certification course in Six sigma(Green Belt). I have not done any other courses or internships. I am also not sure about which specialization I will be taking. However I started to read the books recommended by you to get an insight on business as a whole.
    What are the chances of me getting an admission into one of the top B-Schools if i get a 99.5+?

    Thank you.

    Like

    • Hi Tharun,

      Glad you found the posts useful and they helped you increase your score. Hope the scores only get better!

      If you score in excess of 99.5, with your acads, you stand a pretty good chance of cracking an old IIM!

      So, just stick with the prep, enjoy the prep, the skills you pick up here will be more than crucial in handling the b-school curriculum and getting good grades.

      All the best!

      Like

  6. Saket Lohia says

    Thank You Sir. The posts are really helpful.

    But in the current situation, how do I get to know about better alternative approaches to the quant questions that I solve on a daily basis, because unless I know about that there could be a possibly other time-saving approach to a problem, I just go on solving the problems in a mainstream way. Is there any resource available which I can possibly use to get hold of better approaches or how should I go ahead?

    Like

    • Hi Saket,

      All problems need not have alternate solutions or approaches, so it is actually not possible to get an alternate solution for every problem — just like every ball cannot be late cut, scooped, reverse swept or helicoptered!

      Also, at most, you can look at alternative solutions 50 to 75 problems where someone has come up with an alternative approach, but after that, the question will always be unique and it will be your ability to view solutions in that way that will always get tested. I needed 15 problems to understand the essence of alternate approaches and develop the intent and approach to apply it.

      What is possible though is to increase the solving speed by drastically reducing the writing of steps.

      The cat100percentile.com blog has quite a few posts tagged paperless, those are the best that you can find.

      All the best!

      Like

  7. mayukhsinha07 says

    Hi Sir,

    Thanks a lot Sir for this post, was really the need of the hour for me. I am stuck at 14-15 questions for a long time. I am going to follow this apprach from now on to master it.

    Also, can you elaborate in a post that how does a person increase number of attempts in DILR. For example, Rishi Mittal, 2019 100 percentiler, solved all 8 sets. An avg person like me can solve 3 to 4 sets at max in a standard paper. Is there any way to increase attempts to atleast 5 or 6 sets in a medium difficulty paper in the coming 4 months ? Or an avg guy has the max limit capped at 3-4?

    Thanks in Advance.

    Like

    • Hi Mayukh,

      Glad you found the post useful.

      with respect to DI-LR and solving 8 sets, after a point, the processor speed takes over.

      I have colleagues who do that as well. I admire them but am never intimidated by that since the goal to get a percentile good enough to get calls from old IIMs, not score a hundred percentile.

      It is the difference between saying that I want to be a great batsman with an average over 50 or 52, play 100 plus tests, and be a regular fixture of my side as opposed to saying I want to break Brian Lara’s 400* and 501*. The first goal is achievable, the second depends on circumstances and of course a processor that is an outlier.

      A score of 48, 4 sets right has resulted, in a 99 percentile on DI-LR the last three years; 52 a 99.5 and 60 a 99.95.

      So the first task is to select the easiest 4 sets and solve them flawlessly while not wasting any time scratching around the other 4 sets.

      And then trying to push that to 5.

      A key component of this is the ability to solve the easiest sets super fast. The people who solve 8 are able to do so because they solve the easiest sets super fast and then have time to solve the tough sets. Most people do not have speed on the easiest sets, they take 10 minutes.

      Go through all the posts on DI-LR, I have detailed out selection and execution strategies there.

      And we have a lot more lined up in terms of resources over the last three months of prep.

      All the best!

      Liked by 1 person

  8. Mayukh Sinha says

    I got your point Sir. Using cricket as example really makes it easier to understand. Loved your explanantion.
    Will look forward to read more such amazing blogs.

    Thanks again Sir for helping us out whenever equired!

    Liked by 1 person

  9. Hello Tony,

    This was a very insightful read. Thanks for sharing it with us. I believe the books (you have listed in your previous blog about “Preparing for an MBA not just for the CAT”) will help in analyzing the true aspect of an MBA degree.

    I will be appearing for the CAT 2020. I am an Engineering Grad with 75% marks and 12th and 10th – 93% and 96% respectively with a managerial work-ex of 4+ years. Could you suggest an Institute that would help me build my profile in the HRM or Operations field?

    Thank you 🙂

    Like

  10. Hello Tony,

    This is an insightful read. Thanks for sharing this with us. I believe the books that you have mentioned in your previous blog (Preparing for an MBA and not just the CAT) will help us analyze the right aspect of pursuing an MBA.

    I am an Engineering Grad (2012-2016) with 75% marks, 10th – 12th with 96% and 93% respectively with a relevant managerial experience of 4+ years. The recent pandemic has led me to lose my job and I have decided on appearing for CAT2020. Can you suggest an Institute where I can build my profile in the HRM stream?

    Thank you 🙂

    Like

    • Hi Vignesh,

      The best HR courses in the country are offered by XL, TISS, SIBM, SCMHRD, and XIM-B, there are a few others as well such as MDI-HR, and the IIM-Ranchi MHRM programs.

      So you will have to take the CAT, XAT, SNAP and TISSNET. The major focus should be on the non-CAT exams since all the best HR programs are from the non-CAT exams.

      Hope this clarifies,

      All the best!

      Like

  11. Rajan says

    Greetings sir, your points have been able to drastically changed my approach towards QUANT and I am grateful. However in this post I did not quite understood the
    “Do not algebraify a problem by force” point. Can you provide and example question or clarify the point. Thank You.

    Like

    • Hi Rajan,

      Glad you found the posts useful.

      Well, what I meant is that the first instinct should not be to take the first thing variable you see as X and then try to write an equation.

      This tendency is most visible in TSD, where students want to somehow convert the question into an equation based on S*T = D

      Two towns A and B are 180 kms apart. Car 1 and car 2 start travelling from A and B, respectively towards each other. Their speeds are in the ratio 1 : 2 and they start at 7:00 a.m. and 8:00 a.m., respectively. After meeting at C, they return to their starting positions and again start travelling towards each other. In order to meet car 1 for the second time at C, car 2 halts at C. For how much time does it halt?

      1] 1 hour
      2] 1.5 hours
      3] 2 hours
      4] 3 hours

      In such a problem, the common reaction will be to take the speeds as x and 2x and try to write an equation, whereas the question can be solved without putting pen on paper by just following the logic (option 1)

      Writing an equation is only one of the ways or rather tools to solve a problem, and only in some cases does it become the only way.

      I will do a post titled the elegant solution if I find the time.

      All the best!

      Like

  12. Asmita says

    Hello Sir,
    I am so glad you wrote on this. The post has actually solved my doubt of why i am unable to solve more questions as i clearly got to know its because of my method of solving. I always make sure that i have my pen and paper with me from the moment i start my Quant section. And also as you mentioned above, the tendency to write the redundant data from questions or repeating of steps.
    Thank you for elaborating this topic.

    Like

  13. Asmita Das says

    Hi Sir,

    I have been trying to follow your suggestions and they have improved my scores, thanks a lot for these valuable tips and tricks. One issue with me is that I am not at all good with my retention skills. Could you give me some tips on how to effectively memorize things like powers, fractions, etc., as you mentioned above? Your tips would help me with my general revision as well.

    Thanks in advance!

    Like

    • Hi Asmita,

      I am not an expert on this but the thing I think of for the next three months is to minimise all unnecessary extraneous input — read social media consumption — work on improving your concentration through breathing and meditation exercises — use herbal capsules such as brahmi, ensure that you around your ideal weight +- 5% and include some regular exercise for around 30 minutes that ensures higher oxygen circulation.

      Beyond this your googling is as good as mine.

      All the best!

      Like

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