Official Quant thread for CAT 2013

@ChirpiBird said:
is it 144?
how do u frame the cubes ?

______
| | ------
| 8 | __ | 6 |
| || 2|| |
------------- ------ for max surface area.


_________
| |_2|_
| 8 || 6|
| || |
---------------
for minimum.

i got 608 - 536 = 72..

whatt m missing?

PS : bear with the cumbersome artistry



@rnishant231 said:
how do u frame the cubes ?______| | ------| 8 | __ | 6 || || 2|| |------------- ------ for max surface area._________| |_2|_| 8 || 6|| || |--------------- for minimum.i got 608 - 536 = 72..whatt m missing?PS : bear with the cumbersome artistry
yea, my answer is wrong.. interpreted the question wrong. :mg: :splat:
let me edit it. :)
@2013IsMine said:
8 kareeb hain kya?...x ki value 4.1 approx hain..wahi daal ke ddekh liya....aur kuch nahi samjah aa raha..
Kareeb to hai, but kareeb to bhot answers honge ๐Ÿ˜›
@ScareCrow28 said:
x= 1+ ห†ลก2+ ห†ลก3, then the value of 2x^4 - 8x^3 - 5x^2 + 26x - 28?Copied from CGL 2013 Thread!
x-1=rt2 +rt3
square it
x^2-2x=4+2rt6..............eq1
again square it
x^4 + 4x^2 -4x^3=40+16rt6
Multiply with 2 on both sides
2x^4 + 8x^2 -8x^3=80+32rt6..........eq 2

Multiply eq 1 by 13
then subtract it from eq2, we get
2x^4 - 8x^3 - 5x^2 + 26x=28 + 6rt6
=>2x^4 - 8x^3 - 5x^2 + 26x - 28= 6rt6


@ScareCrow28 said:
Kareeb to hai, but kareeb to bhot answers honge
nahi aa raha bhai..ssc me bhi yeh questions aayenge toh lag jeygi..:P...post karna soiltuion..kal subah dekhta hu..:)
@rnishant231 said:
how do u frame the cubes ?______| | ------| 8 | __ | 6 || || 2|| |------------- ------ for max surface area._________| |_2|_| 8 || 6|| || |--------------- for minimum.i got 608 - 536 = 72..whatt m missing?PS : bear with the cumbersome artistry
Don't need to calculate full area na...

What I did was, the total area of the cubes is some x. Now let's calculate the reduction from x:

If the three cubes all touch each other, there will be 4 surfaces of 2x2 and 2 of 6x6 eliminated

If the 2-waala cube is in the middle and the other two on either side then just 4 surfaces of 2x2 eliminated.

So difference is 2 surfaces of 6x6 => 72.

regards
scrabbler

@scrabbler said:
Don't need to calculate full area na...What I did was, the total area of the cubes is some x. Now let's calculate the reduction from x:If the three cubes all touch each other, there will be 4 surfaces of 2x2 and 2 of 6x6 eliminatedIf the 2-waala cube is in the middle and the other two on either side then just 4 surfaces of 2x2 eliminated.So difference is 2 surfaces of 6x6 => 72.regardsscrabbler

Thought Process
@scrabbler said:
Don't need to calculate full area na...What I did was, the total area of the cubes is some x. Now let's calculate the reduction from x:If the three cubes all touch each other, there will be 4 surfaces of 2x2 and 2 of 6x6 eliminatedIf the 2-waala cube is in the middle and the other two on either side then just 4 surfaces of 2x2 eliminated.So difference is 2 surfaces of 6x6 => 72.regardsscrabbler
you are ultimate dude!! #respect
maine bhi calculate kia, like @rnishant231 did. ๐Ÿ˜ž

@abhishek.2011 said:
let the diameter be 10a+blet oh be xso(10a+b/2 +x)(10a+b/2 -x) = (10b+a/2)^2x = root (11*9(a-b)(a+b))/2as x is a rational number of the form p/q a+b=11a-b=1a=6 b=5diameter 10*6+5=65
@jai.tuteja this the OA

@albiesriram said:
Options? I am getting something like 140...

regards
scrabbler

@scrabbler said:
Options? I am getting something like 140...regardsscrabbler
No options given. But Oa is a notch lower than yours..
Consider, 120,130140 nd 160
@albiesriram said:
qp comes out as root 130
so 130
@albiesriram said:
No options . But Oa is a notch lower than yours..
Haan that's why I wanted options ๐Ÿ˜ Found an approx upper limit and wanted to eliminate. Lazy way out. OK trying for exact answer then :(

Edit: @abhishek.2011 has already posted an answer so...stopped trying ๐Ÿ˜ #sleepy

regards
scrabbler

Again as they quoted earlier , if there is a nobel prize for environment protection it should be given to u. for saving papers..

@scrabbler said:
Haan that's why I wanted options Found an approx upper limit and wanted to eliminate. Lazy way out. OK trying for exact answer then regardsscrabbler
i simply used midpoint rule of medians

a^2+b^2=2(c^2+d^2)
i forgot the name of this identity?
it gives 130 as qp^2 :)

Ptolemy's theorem . @abhishek.2011

One more geometry ,


John has a bag of colored billiard balls which are labeled with the numbers 1,2,3,4,5,6. He reaches into the bag, draws out a ball, records down the number and then places the ball back in the bag. He does this a total of 4 times (hence has 4 numbers). The probability that at least 2 of the numbers are equal is a/b, where a and b are positive, coprime integers. What is the value of a+b?
@bodhi_vriksha said:
My approach : solve it using options ..trying option a ie. 60 ..so take 121 ..we need a weight of 61 kg ..this violates the condition as 60 kg is supposed to be the heaviest ..so A option is rejected ..trying option B.. assume heaviest weight is 62 kg.. to make 118 ..other weight has to be 59 kg... similarly to make 120(62+58),,, so our third weight is 58kg... similarly solving we get fourth and fifth weights as 56 and 55 kg respectively ..Hence our weight s are 62,59,58,56 and 55 kg .. This option B satisfies..Hence B is the answer.Team BV--Pratik Gauri
sir aapke sol me ek error hai... 56 +55 =111 which is not there.
it shud be 54 56 58 59 62........
yes i have found a bug in ur sol..... i can sleep well now...