IIT JEE 2012 - Post Exam Discussion

Well ,the title is obvious. Any thing to share. Personally, I feel that this year's paper was DIFFICULT than the Previous years one. The questions which were doable were lenghtly (not all I mean) and some were really outsmarting.

How do u think?

59 Answers

1
rishabh ·

@mast i marked C & A (acc. to your code),
first is perkins reaction to give unsaturated carboxylic acid → then reduction of double bond then → -COOH to -COCl then → EAS.

this is just my answer.

1708
man111 singh ·

\hspace{-16}(1)\;\; \bf{\int_{-\frac{\pi}{2}}^{\frac{\pi}{2}}\left(x^2+\ln\left(\frac{\pi-x}{\pi+x}\right)\right).\cos xdx}$\\\\\\ (2)\;\; Let $\bf{a_{1}\;a_{2}\;,a_{3},......}$ Be in Harmonic Progression With $\bf{a_{1}=5\;\;,a_{20}=25}$.\\\\ Then Least Positive Int. value of $\bf{n}$ For which $\bf{a_{n}<0}$\\\\\\ (3)\;\; The Eq. of Plane Passing through The point of Intersection of the plane\\\\ $\bf{x+2y+3z=2}$ and $\bf{x-y+z=3}$ at a Distance $\bf{\frac{2}{\sqrt{3}}}$ from $\bf(3,1,-1)$\\\\

1
mast ·

yes , the paper was difficult . i felt physics paper 2 was much difficult than paper 1 also chem was easy though and maths was ok.

1
mast ·

2) n=25

71
Vivek @ Born this Way ·

http://www.resonance.ac.in/reso/news/iitjee-answerkey-solutions.aspx

71
Vivek @ Born this Way ·

And yes Paper 2 was more difficult than the Paper 1. (Most of the students at my center found so)

1708
man111 singh ·

1708
man111 singh ·

For Paper (1)

http://www.prernaclasses.com/IITJEESolutions_2012.htm

1708
man111 singh ·

\hspace{-16}(7)\;\; $Four fair Dice $\bf{D_{1}\;,D_{2}\;,D_{3}\;,D_{4}}$ each having $\bf{6}$ faces no.$\bf{1,2,3,,4,5,6}$\\\\ are Rolled Simultaneously. The Probability that $\bf{D_{4}}$ shows a no. apperaing\\\\ on one of $\bf{D_{1}\;,D_{2}}$ and $\bf{D_{3}}$ is\\\\\\ (8)\;\; If $\bf{P}$ is a $\bf{3\times 3}$ matrix such that $\bf{P^{T}=2P+I}$\\\\ Then There exists a Column Matrix $\bf{X=\begin{bmatrix} \bold{x}\\ \bold{y}\\ \bold{z} \end{bmatrix}\neq\begin{bmatrix} \bold{0}\\ \bold{0}\\ \bold{0} \end{bmatrix}}$. \\\\ Then Which one is Right\\\\ (a) \;\bf{PX=\begin{bmatrix} \bold{0}\\ \bold{0}\\ \bold{0} \end{bmatrix}}\;\;\;\;, (b)\;\;\bf{PX=X}\;\;\;\;,(c)\;\;\bf{PX=2X}\;\;\;\;, (d)\;\;\bf{PX=-X}

1
Aritra Chakrabarti ·

@vivek, man111 how much are you getting in aggregate? what is the cut off?

1708
man111 singh ·

actually I have Completed by B.Tech

I also ask to vivek , aditiya, Rishab, mast and also to you Aritra ,

How Much you guys Getting in IIT-JEE 2012 paper (I) and paper (II)

1708
man111 singh ·

Ans (5) = 4

ans (7) = 91/(216)

1
rishabh ·

@man111: the answers i marked in the exam,
1) π22 - 4
2) 25
3) 5x-11y+z = 17
4) (34Δ)2
5) 4
8) PX = -X

1
mast ·

http://imageshack.us/photo/my-images/189/img1168as.jpg/

1708
man111 singh ·

for paper (II)

http://www.prernaclasses.com/IITJEESolutions_2012.htm

1
samagr@ ·

i havn't seen paper2 yet.Any link??

1
mast ·

thanks

1
rishabh ·

what are you expected marks guys?
i'm in no mood to count.

36
rahul ·

some questions like q4 posted by man111 are more of different thinking than direct solving.....
as in this case Δ2/8 = (3Δ/4)2

and one more wonderful question of co-ordinate (the common tangents to the circles)
is also wonderful....!!!

36
rahul ·

sorry.. Δ2/8 = (3/4Δ)2...!!

1
chessenthus ·

Yes I agree that paper 2 was difficult as compared to paper 1.

1
varun.tinkle ·

@ rahul it is direct solving

write the equation in the form 1-cosp/1+cosp =tan^2p/2 =standard equation wirte it in the form s s-1 s-b s-c.... u get it

and coordinate geo one part two was geometry ..... part on eu can actuallly eliminate 2 options on paper and try with the remianing two

1
varun.tinkle ·

7) i have a nice one line sol

let us calculate the number of cases which icondition is not fullfilled
for that d4-6 values

and d3,d2,d1 =5*5*5
thereofore prop =6*5*5*5/6^4 u get it as 125/216
answer =1-125/216

71
Vivek @ Born this Way ·

For 3, I was getting the first coefficient 5 and 7 but not the latter ones.

1
johncenaiit ·

6) just find the limit of product of the roots of the equation...

you will get it as 1/2...
and only one answer matches....

36
rahul ·

@varun -
ya u r right...
what i did was a bit silly...

2sinA - sin2A2sinA + sin2A = 2 tan2A/2

and in a triangle tan2A/2 = (s - b)(s - c)s (s - a) = s(s - a)(s - b)(s - c){s(s - a)}2 = Δ2/8

rather if i would have multiplied num. and denom. with (s - b)(s - c) then cud get (3/4Δ)2 ...... :P

1
Linkin Park ·

i am getting around 132. bad. what is the cutoff anyway? since it was a tough paper any chance of the cutoffs being around 120.

1
Md. Shahbaz Siddiqi ·

according to the cut off issued by mst coaching institutes it is 143 ..... even i am getting 141

262
Aditya Bhutra ·

cutoff should be around 180 .

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