HOW TO SOLVE MULTIPLE CHOICE QUESTIONS IN IIT-JEE? (part-2)

Click here for Part-1  

First of all, i'd like to apologize to all those who managed to read the part-1 and "actually" waited for part-2. On my part, i can only say that i was quite busy with my life in IIT. Well, without wasting any further time in discussing crap things, let's come straight to the point. So, we were done with 7 shortcuts, here are the remaining few which i remember-

8) Find for n-terms: There are perhaps the easiest kind of questions in maths. Generally, the nth term or sum or product of n-terms is asked. What you can simply do is put the value of n=1,2,3 in the given options and compare with what value will come for 1,2 or 3 terms by simple calculation. Mostly, the answer comes with n=1 or 2. The maximum number of trials required in such questions is 3. If it goes beyond 3, then the question is a high level one and it's better to leave it alone. Example: Sum of n natural numbers (1+2+3+....+n) is
(a) n(n-1)/2;    (b) n(n+1)/2;    (c) n(n+2)/3;     (d) (n+1)(n-1);
Here, the sum of 1 natural number is 1. Now, if you put n=1 in the options, we get;
 (a)=0; (b)=1; (c)=1; (d)=0; Hence, options (a) and (d) can be ruled out. For n=2, the actual answer is (1+2=3). On putting n=2, we get (b)=3; (c)=8/3. Hence, only option-(b) is the correct answer. Similarly, with some practice, you can easily learn how to apply this kind of logic in questions.

9) Generalize the question: This is one of those favorite derivation types questions given in JEE. They will give you a complex orientation and ask you to find one of the variable.what you have to do is assume an orientation such that two or more of the arbitary values go to zero/one/some easy value and then check the options again. Example: suppose for positive real values, it is given that :m³x⁴=n³y⁴  and m²<n²,then

(a) m³x²>n³y² ; (b) m³<y⁴ ; (c) m³x²<n³y² ; (d) m³>y⁴

Now, if you actually start doing the maths of it, you will find yourself in a trouble of inequalities. So better think of an alternative. As we are given necessary conditions for with m and n, so lets assume m=2;x=3;n=3. Thus, you will get y as fourth root of 24 which you can approximate as square root of 5(coz 5x5=25). Now root of 5 is 2.2. For these questions you have to be good at approximating values which is not a big ask (atleast its more natural than remembering all identities). Now put these values in the options. You will easily see that on cancelling the "3" in the options wherever possible, the only option that still stands as correct is option (b) which is the answer.
Similarly, in questions where you are given random inclinations of plane (alpha,beta,etc), see what will happen if the inclination was zero/90. Now put alpha/beta/whatever equal to zero or 90 in the answer and see which of them satisfies the condition. Similarly, for finding moment of inertia about a random axis, same can be appllied.Try this one yourself. Example: Find M.O.I of a rod along an axis at theta degrees from its length passing through the centre.

(a) ML²sin²Ө/12; (b) ML²cos²Ө/12; (c) ML²sinӨcos²Ө/12; (d) ML²sin²ӨcosӨ/12

SOLUTION: Here, we clearly know that M.O.I of a rod along its length is zero. So at Ө=0; M.O.I=0. On putting Ө=0 in options, (a),(c) and (d) become zero. Also M.O.I of a rod perpendicular to its axis i.e. Ө=90 is ML²/12. Now, on putting Ө=90, only option(a) gives ML²/12. Rest all become zero. Simple!! Isn't it?? 

10) Modern Physics (atom,nuclei,radiation,etc): Now this is one topic you would not want to lose marks on. This topic accounts for roughly 20-25 marks in IIT-JEE and you won't need more than a day to expertise this topic even if you start from scratch. If you can't expertise, atleast cram all the formulae related to modern physics. YOU SIMPLY CAN'T LET THE QUESTIONS FROM THIS TOPIC GO AWAY FROM YOU.If you atleast remember all the formulae, you can devise something even in the exam ahll to find the correct option but please DON'T LEAVE IT. Its study requires less than one-tenth of the time required to study "Mechanics" and still it provides marks- 10 times than "Mechanics". STRANGE BUT TRUE!

11) Co-ordinate geometry: This is one area where even a raw but approximate diagram may work in some questions of finding radius, area, equations,etc. Simply draw a diagram according to scale and try to find the required thing. It may seem trivial but it works in many situations. What's the hesitaion in trying something to get to the answer when you don't know the concept? :-p

12) Kinematics, trigonometry: These are the two least weightage topics in JEE. Try to do them as late as possible. It won't even hurt if you leave these topics. They are meant to take up huge volumes of your time and have maximum 2-3 questions in JEE. In the same amount of time, you can score 20-25 marks by studying other topics. YES! IT-IS-TRUE! One may argue that trigonometric basics are used at lots of places elsewhere. My answer is that what you know about trigonometry, by default, is enough to solve the main questions. The tricky ones require use of some identity which only the geekiest of nerds will have idea about. So its better off to leave these topics and concentrate on other areas.

13) Chapter-1 (physics): Remember it? When you enter 11th standard, you have the first chapter about measurements and all which no one cares about. I don't know why no coaching institute pays importance to it. But, this chapter is one easy piece of cherry. Read it thoroughly. You get 3 questions from it about dimensions,maximum error and approximation. If you are not able to understand it from the book, read all the questions from your study material about it. On looking up the answer key, you yourself will eventually figure out the ways to get to the answer of these problems. Remember, on the answer-sheet, only the answer is important. No one cares about the way to get to it. This chapter is just freely distributed marks.

14) NCERT is GOD/GITA/QURAN/BIBLE/WHATEVER:Even my teachers used to say the same when i was in 12th and even i never paid attention to it. But, today i know they said the truth. NCERT is the most precise book esp. in case of CHEMISTRY. In physics and maths, you may find deviations but every question of Chemistry in IIT-JEE is taken from the NCERT book. Read or maybe cram the whole of NCERT (chemistry especially). Most importantly, questions in inorganic chemistry are directly lifted lines from the NCERT.

15) Mind over heart: This happens with the most of us. We see a question in exam and our heart says that the answer is something whereas the mind says something else. Always, go with the mind. The IIT-JEE is meant to test 'intelligence' of over 5 lakh students, not to simply test if something new strikes you during the exam. So, let only the mind solve the questions and let the heart only keep up your spirit. The reverse leads to disaster!

16) Confidence: Whatever happens, this is the most important thing needed during the preparation and exam. Let your spirits always stay high. Remember this fact- " The person writing all this (Dhawal) had only confidence with him. His concepts were zero but still i managed to clear JEE because he believed in himself." And i am not being modest or anything. Neither am i thinking low of myself. I am simply saying the truth in your as well as my face. So, If i can.....anyone can!!
Moreover, never go to the exam centre with any book or anything. The only thing you should be carrying is your admit card and a pencil box with your stationery. And if you feel low while studying, here are some songs that will help lift you up. Put them in your cellphone/ipod and listen over on earphones. I believe it will help you.

Live like you're dying-Kris allen
Firework-Katy Perry
Lose Yourself-Eminem
Remember the name- Fort minor
Someday- Flipsyde
Who says- Selena Gomez (esp for girls) 
 ALL THE BEST FOR YOUR J.E.E..!!! Good luck..!!! Hope i helped you in some way.

P.S: If you are doing engineering just for the namesake of it, then you are committing a grave mistake. All you will end up with is an irritated you. If  you actually are interested in solving question by such methods as i suggested, the C.A.T is the exam for you. In C.A.T coaching, you are officially taught all these methods. :p And, if you have to give C.A.T in the end, then why waste 4 years on a degree that is almost rendered meaningless after M.B.A. So my final word is that- 

"Do engineering if only you are really interested in it. Else please don't waste your life on engineering. Rest is all upto you."

How to solve multiple choice questions in IIT-JEE?

This is ten percent luck, twenty percent skill
Fifteen percent concentrated power of will
Five percent pleasure, fifty percent pain
And a hundred percent reason to remember the name!

“IIT-JEE” – the toughest exam in the world at 18 years of age. Well, lets leave all that blah blah. If you are actually reading this article, then i guess you don’t need to be told anything about it. You already know the numbers – 5 lakh applicants, 2% success rate and all that. Now, in case you have really been studying your ass off for IIT, kudos to you and your courage. Now, let’s get to the point.

I am no stud in the field of engineering studies. I was one of those types who never studied anything seriously. I never followed any textbook (H.C.Verma, loni, M.L.Khanna and all), bunked 70% of my classes and made every possible effort to get to enjoy my life in my +2.  I am the so-called lucky guy who just managed to scrape through into an IIT. Hence, i am no expert to advise people on giving tips to study. But still, if i managed to get through, that means i struck gold somewhere else. That’s what I am discussing here.

For the fact, all the engineering exams in India are objective. Now there are two ways to crack it – either know the concept or know all the wrong answers. In the exam, nobody cares how you circled the bubble. The administrators don’t care if you knew the concept or cheated or circled it blindly or made a fluke. What matters is only the circling of the correct bubble, no matter how you do it. And SENSIBLE GUESSING DOES HELP A LOT IN GAINING THOSE MARKS.

After all, negative marking is just meant to discourage blind guessing only, nothing else. But if you are able to guess sensibly, you will never receive loss due to it. Imagine this yourself - all the exams have 4 options to each questions and, believe it or not, all the answers are equally distributed among all the four options i.e. a, b, c, and d (this is true for all exams- be it your phase test, test series, AIEEE or even IIT-JEE). Now even in the worst case scenario (marking scheme: plus 3,minus 1), if you mark all your blind guesses as, say option-“a”, even then the net difference in your marks will be ZERO.

Surprised!!?? Suppose you made guesses in “x”-number of questions and marked them all as option-“c”. Going by the law of probability, 75% of your guesses will be wrong and 25% will be right. Lets calculate your total by that:

[(X/4) x (+3)] – [(3X/4) x (-1)] =zero. Hence there will be zero addition to your score in the worst case which is true because the administrators never want anyone to lose out because of probability. So they equally distribute the options among all the answers. Now suppose the marking scheme is plus 4, minus 1, as in many exams like DCE, you can actually GAIN 1 MARK for ever four guessed answers by you. Ain’t that free marks??!! :-P

Here are some of the tricks-

1)  Highest and lowest: In a question where numerical values are the answers, the highest and value will never be the correct answers. Weird as it may seem, but it is true for atleast 60% of the cases. So, if you don’t know the way to solve question, try staying away from the extreme values of answers. It might just help you.

2) Two or zero: Whenever in doubt between two of the options, try gambling on one of them. When you have managed to cross out two options, try going for one from the remaining two options. It works.

3) No negatives: For those questions which don’t carry any negative marking (eg: match the following, multiple answers questions which appear ever year in IIT-JEE), go for them even if you don’t even know an inch of the concept. DO NOT EVER LEAVE THEM UNATTEMPTED. If the thing has no discouragements, then why should we be a fool to leave free gambles?

4) Same and different: This applies for those questions which have options in which they play in units and values. Eg: suppose the options for a heat and thermodynamics question are:

(a) 120 K ; (b) 130 C ; (c) 120 C (d) 110 C

Now, since 3 of the options are given in degree Celsius, therefore answer will definitely be in degree Celsius. Now since the value 120 is given in both celsuis and Kelvin, therefore 120 is the numerical answer. Hence, going by the above two logics, the answer will be option-(c) 120 C. Trust me or not, it works in 80% of the cases!

5) Mathematical extremes: Everytime, we do find questions in maths which ask us to either find the range or domain of a function, and the options are generally given as:

(a) [0,1) U (2,3) ; (b) (0,1) U (2,3] ; (c) [0,1] U [2,3] ; (d) (0,1) U (2,3)

As you must have already understood, simply try to test the function on the extreme values i.e.0,1,2,3. You don’t need to solve the whole dam function. Simply see if these 4 values satisfy the function and you will be able to get to the answer.

6) Dimensions: This is one field where the administrators show their complete ignorance. Such types of questions have very stupid options that you feel like laughing on them. Suppose you have a question to find the velocity of an object in an electromagnetic field in some weird orientation with field values as E and B. The options will be something like

(a) (2E/B)^1/2 ; (b) (2B/E) ; (c)  (2E/B) ; (d) (2B/E)^1/2

Now, by simply analysing the dimensions you can tell the answer. Electric field has dimensions (M¹L¹T^-3A^-1) and magnetic field has dimensions (M¹L⁰T^-2A^-1). Simply, you can see that E/B will give you (L¹T^-1) which is dimension of velocity whereas square-root of (E/B) will give root of velocity. Hence, the answer will obviously be option-(c). The “2E” will take care of itself. Dimensional analysis really helps. It helps at a lot of places.

7) Value putting: This applies for questions where we have to find the general expression for something. Suppose you have to find the expression for pressure on a bubble of radius-R when it is at a height h from the ground level in the container which has water upto a height L. (i am just taking a general and easy example, not an exact one.) So, let the options be

(a) P + [pg(L-h)/LR] ; (b) P + [pgLR/(L-h)] ; (c) P + [pgR(L-h)/L] ; (d) P + [pg(L-h)(L-R)/L)

Now, if you would have noticed, you can simply leave out option-(a) by simply checking its dimensions. The dimensions of second term are not that of pressure but of pressure per unit area. Even if you ignore that, we know that pressure at the surface of water must be P and must be (P + pgL) at the base of container. So we have two cases:

At,h=0; pressure=(P + pgL)  and  at,h=L; pressure=P. On putting these two values of “h” in these options, we can clearly see that option-(d) is the correct answer.

(More in next part. Stay tuned)

In case you want to test all these things, take up an MCQ set of a topic which you have not studied and try all these logincs on those questions and see the score that you get. I indirectly practiced these things and they really helped me. I got 30 extra marks in IIT-JEE by the same approach!!

Well, now i am a bit tired by writing and need some sleep too. So I am stopping here. The next part will be out in 4-5 days. In case you liked the post, please comment and give your feedback. In case you want any advice, you can contact me at my email id on my blog profile. Remember, the exam tries to test our knowledge and understanding, but sometimes it just forgets to maintain the logic in the options. (^_^) (*_*)

Click here for Part-2