CAT 2016: Quant for CAT; Logic Vs Shortcuts - how to prepare, expert tips

CAT 2016, on the same pattern of 2015 exam proposes to have MCQs with negative marking and Non-MCQs without negative marking in Quantitative Aptitude section. The only difference between the last year CAT and CAT 2016 is that number of questions has not been revealed by IIM Bangalore for CAT 2016 whereas in 2015 details about the number of total and sectional division of questions was made available along with the release of CAT notification.
However, non-availability of exact information about the number of questions in Quant section should not be an obstacle in preparation for this section in CAT 2016. In this article, Prof Nishit K. Sinha an IIM Lucknow alumnus,who has been training students for the CAT and other B-school entrance examinations for around 15 years and author of titles for CAT preparation QA for CAT, LRDI for CAT, VARC for CAT published by Pearson publications, shares the strategy how prepare Quant for CAT 2016.

Logic Vs shortcut
Prof Sinha shares During the last 15-odd years of training students for CAT preparation, I have been asked many times Can we bank upon shortcuts to get a decent percentile in CAT? Is it really required to be able to analyze the topics well before we are able to solve a question? In case my application of concepts is not strong, can I just mug up the formula for solving the question?
To answer these questions, let me take you through Blooms taxonomy, which is an established and accepted form of learning hierarchy. Following is the presentation of Blooms taxonomy:
CREATING --> EVALUATING --> ANALYSING --> APPLYING --> UNDERSTANDING --> REMEMBERING
At the base of Blooms taxonomy are basics of learning Remembering and Understanding. All the levels above this Applying, Analyzing, Evaluating and Creating are considered Higher Order thinking. To solve questions at this level, you need to have a sound thought process and strong logical abilities.

CAT 2016: Dont expect Qs of Creating Level
CAT is a self-professed test of Higher Order Thinking. To achieve a high score in CAT, it is important to understand the relative importance of different layers as above. While you will not get any question at the Creating Level, you may get a maximum of 10% of the total QA question at 1st level which will translate into a maximum three questions as per CAT 2016 pattern. These questions may be done by simply going through the formula. In other words, to be able to solve the remaining questions you need to move up the hierarchy.

If you make an analogy between CAT Quant paper and learning objectives as shown in Blooms taxonomy, following is a realistic break up:
Evaluating - 4-5 Qns --> Analyzing - 7-8 Qns --> Applying - 10-11 Qns --> Understanding - 7-8 Qns --> Remembering - 3 Qns
Prof Sinha clarifies For the sake of creating a level playing field, I am using concept of Simple Interest and Compound Interest to elucidate all the Learning Objectives. Let us understand these with the help of examples:

Level 1 Remembering
Q. If Principal = Rs. 1000, Rate of Interest = 20% and Time = 2 years, what is the Simple Interest?
--> To solve this question, you just need to know the formula for calculating Simple Interest (SI). SI = PRT/100 = 1000x20x2/100 = Rs. 400

Level 2 Understanding
Q. At simple interest, a sum of money amounts to three times the original value in four years. How many times the original value will it amount to in 16 years?
Solution Amount follows Arithmetic Progression in case of Simple Interest.

Using this:
Assume Principal = Rs. 100.
According to the question, Rs 100 --4 years-- Rs 300
It will follow the following pattern now:
Rs 100 -- 4 Years --> Rs 300 -- Next 4 Years --> Rs 500 -- Next 4 Years --> Rs 700 -- Next 4 Years --> Rs 900
Hence in 16 years, it will amount to 9 times the original value.

Level 3 - Applying
Q. At SI, a sum of money amounts to Rs. 2600 in three years and Rs. 3000 in next two years. What is the rate of interest?
Solution You may observe that to solve this question, you cannot use any formula or short cut. You need to have an understanding of how Simple Interest works and be able to apply the same.
There are two data points in this question:

Amount at the end of three years = Rs. 2600 and amount in next two years (i.e. total five years) = Rs. 3000.
Using this, it can be inferred that:
Interest obtained in last two years = Rs. 400 Interest obtained per year = 400/2 = Rs. 200 per year.
Hence interest obtained in three years = Rs. 200 3 = Rs. 600
So principal = Rs. 2600 Rs. 600 = Rs. 2000
Hence rate of interest = 200/2000 100 = 10%

Level 4 Analyzing
Q. Equal sum have been invested at CI and SI at same rate of interest. At the end of two years, total SI obtained = Rs. 500 and total CI obtained = Rs. 550. What is the sum invested at SI or at CI?
Solution Analyzing is ability to know where to start the problem solving from, then breaking down the problem in smaller parts leading to the most important aspect of the problem.
To solve this question, you are required to understand how SI and CI are calculated, apply the conceptual framework of SI and CI after breaking down the problem in smaller parts.

Where to start solving this problem:
Using the data for CI will not lead you to any conclusion regarding the interest obtained in 1st year or 2nd year.
Using the data for SI: Since total interest obtained in two years = Rs. 500, interest obtained in the 1st year = Interest obtained in the 2nd year = Rs. 250 each.
Simple interest obtained in the 1st year = Compound interest obtained in the 1st year (Since Principal is same) = Rs. 250. Hence CI for 2nd year = Rs. 550 Rs. 250 = Rs. 300
It can be summarized here:

1st Year
2nd Year
Simple Interest
Rs. 250
Rs. 250

Compound Interest
Rs. 250
Rs. 300

Hence rate of interest = 50/250 100 = 20%

Got it or not: Shortcut not much helpful
According to Prof Sinha Summarizing this whole article, in Quant, you may be able to solve a maximum of 5-6 questions using short cut or tricks, which is certainly NOT sufficient to get you a good percentile in CAT 2016. To move into higher percentile zone, you need to develop logical ability to apply and analyze the concepts.

You should learn the basics of concepts, and get into the higher order thinking Applying Analyzing Evaluating.