# How to crack the DI-LR section of the CAT – II

In the previous post, we took up 6 of the 8 sets from the DI-LR section CAT 2017 Slot 2 and took a call on which ones solve and also looked at the best way of solving the same. In this post, we will look at the remaining two sets and also what is making the DI-LR sections on recent CATs unique.

## It’s no longer DI-LR but Math-LR!

One of the things I like to do when I teach is to show students the inner workings of the machine that is a question or a set. As the old adage goes, one should teach people to fish rather than give them fish. To do that one should first know more about fish than about fishing!

So I took a lot of time looking at these DI-LR sets, trying to figure out why they are creating problems for test-takers.

In cricket, we often have mystery bowlers springing up on to the scene who in a short span of time wreak havoc on batsmen of all stripes, most of them also disappear suddenly — the Lankan spinner Ajantha Mendis epitomized this phenomenon.

Why do they cause so much destruction? Because they defy expectation and test a different kind of skill or mindset that most batsmen take time to figure out.

The DI-LR sets have been defying the two expectations that test-takers have come to expect when they hear the word DI-LR — calculation and reasoning.

All of you know by now that calculation in the classical sense of breaking numbers down has come down. But what most test-takers haven’t seen is that reasoning in the classical sense has also disappeared.

When we think reasoning we think of it in terms of solving puzzles.

But if we take a look at all the sets, barring The Pizza Set, on the DI-LR section of CAT 2017  Slot 2, they have moved to a new area — Mathematical Reasoning or reasoning in a Math context.

What do I mean by this?

If we can think of an LR set as an equation where the variables are on the LHS and the conditions are on the RHS, earlier the RHS was pure logical constraint, now the RHS is a number!

The LHS has always been the various possibilities and using the RHS we eliminated possibilities.

When the RHS becomes a number, the LHS also becomes a series of numerical possibilities!

Let us look at the sets to get a fair idea:

The Old Woman and her Wealth

The amount of 210 lakhs had to be divided equally and hence the RHS becomes 70 each. Now you have to try out different number combinations, eliminate the ones that contradict conditions and arrive at the answer. This is how we solved the first two questions in the set, we eliminated numbers.

What about questions 3 and 4 in that set?

Q.11) The value of the assets distributed among Neeta, Seeta and Geeta was in the ratio of 1:2:3, while the gold coins were distributed among them in the ratio of 2:3:4. One child got all three flats and she did not get the house. One child, other than Geeta, got Rs. 30 lakh in bank deposits. How many gold coins did the old woman have?

Q.12) The value of the assets distributed among Neeta, Seeta and Geeta was in the ratio of 1:2:3, while the gold coins were distributed among them in the ratio of 2:3:4. One child got all three flats and she did not get the house. One child, other than Geeta, got Rs. 30 lakh in bank deposits. How much did Geeta get in bank deposits (in lakhs of rupees)?

It is so obvious that they are purely Arithmetic questions!

There is no way anyone can argue that the two questions cannot be part of the QA section. Just because a question is long does not mean that it becomes an LR question.

The Dormitory Set

The first two questions were pure LR questions but what about the next two?

1. 4 of the 10 dorms needing repair are women’s dorms and need a total of Rs. 20 Crores for repair.
2. Only one of Dorms 1 to 5 is a women’s dorm.

Q 15) What is the cost for repairing Dorm 9 (in Rs. Crores)?

Q 16) Which of the following is a women’s dorm?

20 Crores has to be divided into 4 dorms and the numbers available are 1, 2, 3, 4, 5 and 6.

Only those with a good grasp of averages can see that since the maximum number you have is 6, you have to first give as many 5s and 6s as possible.

This again pushes the set into the realm of Math LR.

The Cup of Tea

This is a simple set but the anchor condition gives you a set of 5 pairs of numbers of which you have to eliminate 4 using other numerical conditions.

None of these sets were pure LR sets that did not involve numbers.

The two sets that are left will illustrate even more clearly the concept of Math-LR set.

## The Airplane Seating

Eight friends: Ajit, Byomkesh, Gargi, Jayanta, Kikira, Manik, Prodosh and Tapesh are going to Delhi from Kolkata by a flight operated by Cheap Air. In the flight, sitting is arranged in 30 rows, numbered 1 to 30, each consisting of 6 seats, marked by letters A to F from left to right, respectively. Seats A to C, are to the left of the aisle (the passage running from the front of the aircraft to the back), and seats D to F, are to the right of the aisle. Seats A and F are by the windows and referred to as Window seats, C and D are by the aisle and are referred to as Aisle seats while B and E are referred to as Middle seats. Seats marked by consecutive letters are called consecutive seats (or seats next to each other). A seat number is a combination of the row number, followed by the letter indicating the position in the row; e.g., 1A is the left window seat in the first row, while 12E is the right middle seat in the 12th row.

Cheap Air charges Rs. 1000 extra for any seats in Rows 1, 12 and 13 as those have extra legroom. For Rows 2-10, it charges Rs. 300 extra for Window seats and Rs. 500 extra for Aisle seats. For Rows 11 and 14 to 20, it charges Rs. 200 extra for Window seats and Rs. 400 extra for Aisle seats. All other seats are available at no extra charge.

The following are known:

1. The eight friends were seated in six different rows.
2. They occupied 3 Window seats, 4 Aisle seats, and 1 Middle seat.
3. Seven of them had to pay extra amounts, totaling to Rs. 4600, for their choices of seats. One of them did not pay any additional amount for his/her choice of seat.
4. Jayanta, Ajit, and Byomkesh were sitting in seats marked by the same letter, in consecutive rows in increasing order of row numbers; but all of them paid different amounts for their choices of seats. One of these amounts may be zero.
5. Gargi was sitting next to Kikira, and Manik was sitting next to Jayanta.
6. Prodosh and Tapesh were sitting in seats marked by the same letter, in consecutive rows in increasing order of row numbers; but they paid different amounts for their choices of seats. One of these amounts may be zero.

Look at the anchor condition — it’s purely a mathematical condition.

Just like 210 lakhs, and 20 crores in the previous sets, in this one, it is 4600.

You have to divide 4600 among 7 people using the numbers, 1000, 500, 400, 300 and 200.

The biggest mistake that test-takers can make while solving this set is to start by trying to arrange people into seats.

As in if you start with the arrangement and then try to fit the Math into it. Nothing can lead you to waste more time and get stuck than this. And if this set came right at the beginning for you then you have had it.

What you need to do is to start by changing your mindset — put the Math before the LR. The way Aravinda De Silva, for example, was very successful against Anil Kumble because he did not treat him like a spinner but like a medium-pacer.

How do you go about putting the Math first?

4600 divided by 7 means an average of around 650. Since the average is closer to 500 than to 1000 there will be more 500s and under than 1000s. So more 500s than 1000s out of 7 means the division can be 4-3 or 5-2. It is always best to test the boundary conditions, that is the lower side first.

Can you have two 1000s? If you have two 1000s then the balance is 2600 over 5 people making the average over 500. If the maximum value is 500 then you cannot have an average of over 500!

So it has to be three 1000s.

Once you have three 1000s how can you make the remaining 1600 using 4 numbers?

• Option 1 — 500, 500, 400, 200
• Option 2 — 500, 500, 300, 300
• Option 3 — 400, 400, 400, 400

The next big condition says that you have three people in consecutive seats with 3 different prices, so they are either 3 different aisles or three different windows.

So the only combinations can be 1000, 500, 400 or 1000, 300, 200.

This straightway eliminates options 2 and 3.

Once you do this the rest of the set opens up easily.

• 4 Aisle, 3 Windows and 1 middle
• You need 3 seats with same letters and 2 seats with same letters with different numbers
• You have 1000 (A/W), 1000 (1000A/W), 1000 (A/W), 500 (A), 500 (A), 400 (A) and 200(W)
• Since you have only two different values for Windows — 1000 and 200 — it has to be 3 consecutive Aisles and 2 Consecutive Windows.
• If you have 2 consecutive windows but only one value of 200, then it means that one guy paid and the other had a seat that
• wasn’t chargeable and was immediately after the paid 200 seat.
• 200s are from 14 to 20, so the two consecutive seats have to be 20W and 21W, Prodosh and Tapesh
• The three consecutive aisle seats with different rates have to be 500, 400 and 1000 the only possible combination is 10A, 11A & 12A — Jayant (500), Ajit (400) & Byomkesh (1000) (I have used ‘A’ to represent an aisle and not the letter of the seat).
• Out of the 7 numbers you have assigned 4
• The three left are 1000, 1000 and 500.
• Two more people are next to each other and they have to be the two 1000s
• Manik is next to Jayanta but if he takes the middle he will be not paying anything but we already have one person who is not paying anything.
• So he is sitting next to Jayanta but on the aisle next to him by paying 500
• All 4 Aisles are done, and 2 out of 3 Windows are done and 1 middle is left.
• So, Gargi and Kikira occupy a Window and a Middle that cost 1000 each, in either row 1 or row 13

Q.25) In which row was Manik sitting?

1. 10
2. 11
3. 12
4. 13

Q.26) How much extra did Jayanta pay for his choice of seat?

1. Rs. 300
2. Rs. 400
3. Rs. 500
4. Rs. 1000

Q.27) How much extra did Gargi pay for her choice of seat?

1. 0
2. Rs. 300
3. Rs. 400
4. Rs. 1000

Q.28) Who among the following did not pay any extra amount for his/her choice of seat?

1. Kikira
2. Manik
3. Gargi
4. Tapesh

You have all the answers and you are only left wondering who came up with the names Prodosh and Kimura!

If you see, unlike a typical LR set you can solve all the questions without drawing (This is what makes it a classic Math-LR Set.

Some of you might have cracked this set using drawing. I am not saying you should not draw but I am saying is that you should add the skill of putting Math before LR to your repertoire.

## The Fingerprint Set

A high-security research lab requires the researchers to set a passkey sequence based on the scan of the five fingers of their left hands. When an employee first joins the lab, her fingers are scanned in an order of her choice, and then when she wants to re-enter the facility, she has to scan the five fingers in the same sequence.

The lab authorities are considering some relaxations of the scan order requirements since it is observed that some employees often get locked-out because they forget the sequence.

Q.29) The lab has decided to allow a variation in the sequence of scans of the five fingers so that at most two scans (out of five) are out of place. For example, if the original sequence is Thumb (T), index finger (I), middle finger (M), ring finger (R) and little finger (L) then TLMRI is also allowed, but TMRLI is not.

How many different sequences of scans are allowed for any given person’s original scan?

Enter your response (as an integer) using the virtual keyboard.

For any given key if two letters can be out of place then how many ways can we choose those two letters out of 5 letters? 5C2 or 10 pairs can be out of place and still be valid. So including the original combination, one can have 11 valid passkeys.

This entire set is built on the bedrock of P&C. It is no surprise that my colleague VK, whom most of you would have seen during the LMTC sessions or know from his website vkpedia, found this set very easy since he is a champ at P&C.

On such a DI-LR section, those who are naturally good at QA, especially the Number Systems experts should have cleared the cut-offs without much trouble. Those who are primarily good at VA-RC, Arithmetic, and LR, would have struggled or just fallen short of the cut-off.

## There are no closed sets

Another feature of these sets is that none of them are closed.

• The Pizza Set — With the given information you still do not know anything about EC or DD
• The Dormitory Set — You do not know where rooms 2 and 10 fit in or the specific costs of rooms, 1, 3, 5 & 9
• The Old Woman and her Wealth — everything is open
• The Chess Set — everything is open
• A Cup of Tea — the places of 4 cups are unknown
• The Airplane Seating — the rows of Gargi and Kikira or the specific seat numbers of the aisle people.
• The Fingerprint Set — everything is open

It is now easy to see why these sets are causing trouble or taking a lot of time — they are Open Sets based on Math and this is the exact opposite of what test-takers like and want — Closed sets based on Arrangement.

## Developing the fast-twitch muscle in the brain

One of the key requirements to be good at solving LR sets such as The Dormitory Set or even The Airplane Set is to be able to quickly list alternatives, keep moving from one condition to the other and keep eliminating options.

This is very different from LR sets where you do not have to list alternatives but only work the conditions.

I find the former skill very similar to solving Sudoku. One has to keep moving very dynamically across cells and keep arriving at the number by the process of elimination.

Even before I began solving all of these sets, I felt that I needed to get my brain warmed up and supple. I felt that I since I haven’t solved LR sets in a while I would need to get the blood pumping through the gray cells. So I did what works best for me a few Sudoku sets on my phone till I knew that I was moving absolutely smoothly without getting stuck.

My favourite batsman, Brian Lara, was known to have a net or play some TT during the breaks between innings, especially if he was in good nick and scoring fast, he just didn’t want to let go of the rhythm and quick reflexes.

I would strongly advise solving 3 medium-level Sudoku sets a day targeting an average time of 4 mins per set. On every third day, you should take up a difficult set so that you push yourself a bit harder.

## Don’t expect sets to yield with you on auto-pilot

The brain like the body wants to be on auto-pilot mode. This means that it is traversing familiar territory and hence will execute the motions it has perfected already with considerable ease. Think of this as playing on an ODI or T20I pitch where the ball and the bowler cannot surprise you because the pitch does give them any purchase.

And what is tough is usually so because it is unique. And unique means that you cannot be on autopilot. Think of this as batting on a worsening pitch in the fourth innings — the same limited overs heroes struggle to chase down 250 in a day (it’s not the format but the skill sets that have become limited, which why our Indian team manager’s talk on recent international test tours about intent is doesn’t translate into runs).

If you make this change in your head then you know what you are up against.

## The ability to think deeply and with clarity

Chasing down a total, not just surviving, on a fourth innings pitch means that you have to concentrate hard.

The ability to think deeply means that when you read a set you are figuring out the complexity of the set and really understanding it in terms of how to represent it.

The core skill would be the ability of your brain to focus deeply and for long without getting tired or distracted.

The best way to do this by ensuring that all your prep sessions are for 3 hours with your phone switched off. If you are prepping with your phone on then I am afraid that you are doing yourself a great disservice.

I always know how likely I am to do a set correctly and in good time based on how fresh and relaxed my brain is feeling.

So one of the things that you should ensure over the next two months when you will be taking a lot of tests is that you conserve your mental energy.

While you might think that watching your favorite TV show or browsing social media for an hour or so is relaxing, it is taxing your eyes with light from the screen. I would rather suggest a nap or a walk as the ideal rest or break.

Also, do not forget to do some form of exercise regularly since it increases the oxygen supply in the system. I know of a few people for whom none of this will matter but as I said I know only a few and I am not one of them.

There is no point in looking for exactly these kind of sets to solve since you will never get mirror replicas. I would rather suggest that you resolve all the sets from the SimCATs keeping in mind the following things:

• rate the set before solving
• figure out the best way of representing instead of blindly jumping to draw something
• identify the anchor conditions and learn to work with them
• keep moving between conditions and eliminating instead of getting stuck in your table
• identify the Math-LR sets and execute putting the Math first

Becoming good at something is always about doing 10 small things right. Most of the time people think it is one big thing that they lack and that couldn’t be farther from the truth.

1. Rahul Nandu says

Hello sir,
Sir i am at the ground level with my preparation and getting around 60 percentile in SIMCAT, so please suggest me that bow should i prepare in coming days to maximise my scores. I am unable to figure out that how should i study now. Please guide me sit.

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• Hi Rahul,

This is what you should do:

1. If you are really weak in Math, as in you do not know anything, then there is no option but to start from the printed study material.
2. If you are comfortable with Math and just need a quick brush-up then go through the QA Masterclasses in the Videos section of myIMS.
3. Parallelly, view the Masterclasses on DI-LR, VA, and RC.
4. After this start solving 3 sets of each every day from the BRM or from the e-concept builder, C Module of myIMS, if you feel the level is low then jump to the Application Builder, the A Module of myIMS. For QA solve questions by Area, start with Arithmetic, followed by Geometry and Modern Math, do number systems at the end.

Take at least one test a week in September, two a week in October, and three a week in November.

Hope this helps,

All the best!

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2. Rahul Nandu says

Thank you sir, i will follow this. Sir i feel a bit nervous with my current level of preparation, it’s not too late na sir..?

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• That you will only know once the test is done! You have no option but to go ahead full steam now.

All the best!

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3. mukul says

first of all, very enlightening post sir,really appreciate it..changed my mindset towards dilr solving.

sir i have been preparing from long time for cat. i’m enrolled in a online program for cat prep…i barley got to 60’s in full length tests.. and lil better in sectionals..but suddenly i don’t know what happened i’m running into amnesia of confidence,and feeling hopeless and that in turn have left me performing me like i never studied for cat..it’s like i’m ruining into amnesia of things i even knew before and …even though trying all things like deleting myself from social media, staying at home studying all day from the time i wake up to the time i go to bed..heck! i even changed from listing rap music to Mozart ..but still i’m not making progress..i had bad dreams taking away my breath in middle of night that i didn’t got it this year as well(my 3rd attempt),probably my last chance .however i can’t allow myself to give up, but i have no idea is there still possibility for me to achieve what i wanted to be in just 2 months?

Like

• Hi Mukul,
Maybe the problem is that you have been preparing so hard for so long that your mind needs a break. Too much of anything without a break can be harmful or rather thinking about one thing for too long and too intensely (changing music) will lead to diminishing returns. So what I suggest is this:

1. Take a break of a week and do a small trip with friends (do not go alone, it is more of just your own mind). Forget everything about CAT for a while, release the pressure you have built up, enjoy yourself sensibly.

2. Come back and prep but make a provision for fun, listen to the music you like, one should be hard on oneself but not bahut hard 🙂

3. Read all the CAT Strat posts on this blog — VA, QA and DI-LR, basically the last 10 posts. Read it not to consume gyaan but to implement.

4. Set a simple target for each mock, the first target should be 75 — 25 in each section but done efficiently through selecting the right questions and sets across the three sections and not the way you have been solving till date. no matter what your level, you have to implement the selection methods I discuss, purely because even at a score of 120 you will be leaving more questions that you will attempt, what matters is to leave the right questions without any time left.

5. Build a certain amount of time to step out into the open every day and more importantly meet friends once in a while. Make a plan and incorporate the breaks into it.

You will make it, just focus on executing the selection plans and everything else that I talk about in the whole blog.

Hope this helps,

All the best!

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4. Hello sir, as you told us at LMTC in Delhi that there will be 150+ concept videos available in our portal from 15 September . Can you tell us when we will have access to those videos?

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You will get access to a new different website (along with the old one) by tomorrow.
All the best!

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5. Nitin gulati says

A very good morning sir!!!
Just a small request, it would be of great help if you make a video on strategy to tackel DI-LR section.
As I have gone through your post on di-lr , and also I was not able to attend the LMTC delhi.

So if it will be posssible it will be the greatest help for my prep.

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• We are doing videos of entire LMTC fir the rest of the country, Oct-10, release.

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6. Sanju Sharma says

Hi Sir,
I’m comfortable in doing most of the LR sets but it takes a lot of time for me to solve one. After the mocks i see that at around 6 out of 8 sets were doable for me but i could only attempt 3 or 4 at max.
Now going back to the material questions seems like a futile effort to increase the speed. What should i do?

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• Hi Sanju,

While 6 sets are doable, given the time constraints very few, people are able to solve 5 sets correctly, only those scoring 99.95 to precise.

In the last two years, 3 sets will have got you a 95 and 4 a 99.5, so aim for a score above 40 and you will get a percentile above 99 in DI.

If you select the right sets, 10 minutes to select, you should take 12 minutes per set for the 4 easiest sets and solve them in 50 minutes.

All the best!

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7. Mohan Kumar says

Dear Sir,

I am been through all last 4 posts on DI-LR and also attended LTC.
Both the posts and LTC are really very helpful.

My last 3 SIMCATs DI_LR score are SIMCAT 11 – 2 (Total 48), SIMCAT 9 – 8 (Total 66) , SIMCAT 8 – 23 (Total 92)

I tried to analyse what could have gone wrong and I feel it the selection of sets which made all problem. If I am doing in my home without time constraints then 6-7 sets I am able to solve without any help but in around 20-30 mins each. I further tried to see why my selection might be going wrong but i am not able to come to a proper conclusion for this.

What exactly is happening with me is this –
1. To mark set out of 3 (1-2-3) – Most of my sets are 2 and few are 3 and none/very less are 1 because they don’t really feel like unique. And I have not solved many sets till now so very less 3.
2. To mark conditions out of 3 – Majority of times conditions are either rules or a mix of P-D so conditions take 2.
3. To mark questions out of 4 – Now this is where my all marking depends on because sometimes all 4 questions are like what is the value of X with one option as Cannot be determined to these type of question I marks 4. Sometimes they are just all open questions which give some more information about the set which I mark 0. Sometimes a mix of direct and open I mark accordingly and rarely there do we get all 4 questions with no range and no Cannot be determined.

Below I have listed my marking of SIMCAT 11-
No Set Conditions Questions Total
1 2 2 2/1 6/5
2 2 2/1 4 8/7
3 1 2 4 7
4 2/3 3 2 6/7
5 2 2 4 8
6 2/3 2/3 4 8/9
7 2/3 2 0 4/5
8 2 2 0 4

What went wrong was marking of sets took around 13-15mins and though I started with the set marked 8 or above I was not able to crack the set within 12-15 mins so I changed my set and then the same thing happened again.

I am not able to figure out how can i improve my marks.

It will be of really great help to me if you could pls advice what might be going wrong or how should I improve myself.

Thanking you,
Mohan Kumar

On a side note – Regarding Airplane arrangement seating set –
From this point “Once you have three 1000s how can you make the remaining 1600 using 4 numbers?” you have listed only 3 possibilities (Option 1 — 500, 500, 400, 200; Option 2 — 500, 500, 300, 300; Option 3 — 400, 400, 400, 400) whereas I feel another possibility (500, 400, 400 300) should also be considered and based on conditions given we need to make 2 cases and then eliminate this possibility.

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• Hi Mohan,

I think even if you get the selection right 20 minutes per set is way too high and you have said that you have not practiced much. So may be the first task is to get about 100 sets under your belt, use the section tests and some of the 25 take home tests, that can now be converted into section tests. It will help you both with speed and selection.

In the meantime, I’ll take a look at SimCAT 11 and give my classification for the same.

All the best!

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• Mohan Kumar says

Sure sir. I have started working on more set, will go through Section/Take-home tests.

Classification would be indeed very helpful.

Thank you Sir

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• I just solved the DI-LR section and I think it was really, really well-designed — seemingly every set was do-able but every set was tricky. This was my classification.

Set 1: Management Institute — 3/2/3 — 8
Set 2: Mobile Phones — 3/0/4 — 7
Set 3: Coins Sharing — 1/1/4 — 6
Set 4: Grocery Shopping — 1/2/4 — 7
Set 5: School Boards — 3/3/2 — 8
Set 6: Conference — 3/1/4 — 8
Set 7: Time Zone — 3/3/4 — 10
Set 8: Football Cup — 3/2/0 — 5

For the Time Zone Set, I gave a 3 and 3 to the set and conditions since they are as direct as it can get and I can easily calculate the travel times. I gave a 4 to the questions despite being open since there is no other way to ask a question to such a set, otherwise, the questions become too direct and even then also there are only two questions that can be asked based on the set, the travel times between the two pairs of cities.

I have seen so many sets of the Mobile Phone type that I know that the set will be super time-consuming.

Coins Sharing conditions gave me nothing and so I rated it a 1.

As far Cannot be Determined goes, I take such questions as closed questions since I will have blanks in my table, and I always suspect that they are selling me a dummy.

I solved Time Zone, Management Insitute, School Boards, and Grocery Shopping in that order.

Hope this clarifies,

All the best!

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8. Tanya says

Hello Sir, I have a doubt regarding the solving of DI-LR sums. So I have just started preparing and in general DI LR has been smooth for me. In the test scenario, I am able to solve 3-4 sets. But I know I can solve more. However, most of my time goes into how to start solving the question. When I see the solution I realize I could have done the set only if I had known how to start. Because once I see the starting step, I am able to solve the rest of the set easily. Do you think there’s any way of tackling this problem?

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• Hi Tanya,

3-4 sets in a SimCAT is pretty good at this stage as long as you are choosing the right sets.

Since you have just started off it will be a while before you solve enough Take-Home SimCATs and Proctored SimCATs, for you to instinctively start reaching the start earlier. Think of your brain itself as a machine that is learning, the more the that goes in the better it will get.

All the best!

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