Official Quant thread for CAT 2013

catter2011 · November 17, 2012, 9:43am

@ayushnasa said:
@catter2011 @rachit_28 Bhaiyo, aise hi answers par mat pahucho...Check for 1 or more cases first...Agar 6 log hai, n=2 and m=4 aise me thode hi fit hoga??

ur crct.. but 6 cases is hard and time consuming.. we can move ahead with (1,1) and (2,1) cases.. dats enough.. to crack options.. waise wats the OA in m,n terms ?

catter2011 · November 17, 2012, 9:44am

@ScareCrow28 said:
OA: (n-m)/(n+m)

i am getting (1- ur OA), i gave a valid case above (taking 3 persons a,b,c).. can you please correct it ?

ayushnasa · November 17, 2012, 9:44am

@ScareCrow28 said:
OA: (n-m)/(n+m)

Take n=1, m=1 Then answer should be 1/2. But by this OA, we get 0....This has to have some error

catter2011 · November 17, 2012, 9:45am

@ayushnasa said:
Take n=1, m=. Then one case solves the change problem, one doesn't. So answer should be 1/2. But by this OA, we get 0....This has to hace some error

i guess answer is 2m/n+m,

ayushnasa · November 17, 2012, 9:48am

@catter2011 said:
i guess answer is 2m/n+m,

with n=3, m=1 we get answer as 3/4 and your method would yield 2/4

catter2011 · November 17, 2012, 9:48am

@ScareCrow28 please post how did u get (n-m)/(n+m), though the actual solution.. not taking assumptions..

chillfactor · November 17, 2012, 9:49am

@ScareCrow28 said:
A queue of n + m people is waiting at a box office; n of them have 5-pound notes and m have 10-pound notes. The tickets cost 5 pounds each. When the box office opens there is no money in the till. If each customer buys just one ticket, what is the probability that none of them will have to wait for change?

Its application of catalan numbers (check this link for details:- http://en.wikipedia.org/wiki/Catalan_number

Probability = 1 - {C(m + n, n + 1)/C(m + n, n)} = 1 - m/(n + 1) = (n - m + 1)/(n + 1)

scarecrow28 · November 17, 2012, 9:49am

@catter2011 said:
i guess answer is 2m/n+m,

If we take n=1 and m=1..prob should be 1/2

But acc to ur ans..it's 2/2 = 1 (Not Possible)

I can't validate the correctness of the OA but..I do think either the OA needs correction or our theories..

ayushnasa · November 17, 2012, 9:51am

@chillfactor said:
Its application of catalan numbers (check this link for details:- en.wikipedia.org/wiki/Catalan_...Probability = 1 - {C(m + n, n + 1)/C(m + n, n)} = 1 - m/(n + 1) = (n - m + 1)/(n + 1)

THIS is correct...

scarecrow28 · November 17, 2012, 9:52am

@chillfactor said:
Its application of catalan numbers (check this link for details:- en.wikipedia.org/wiki/Catalan_...Probability = 1 - {C(m + n, n + 1)/C(m + n, n)} = 1 - m/(n + 1) = (n - m + 1)/(n + 1)

Sir if you can explain in detail then please do 😞 I don't want to open that webpage..it's too scary

catter2011 · November 17, 2012, 9:54am

@ayushnasa said:
THIS is correct...

thanks.... yeah. dats the OA. substitution is best process.. though i guessed. assuming these guys answers.. i got wrong finally..

chillfactor · November 17, 2012, 9:56am

@ScareCrow28 said:
Sir if you can explain in detail then please do I don't want to open that webpage..it's too scary

Its not possible to explain it here (atleast I can't do it), check the link.

Actually no need to do all these things, even if a question is asked on the same logic, then the numbers will be smaller which can counted manually. In case you wanna learn I would say that you should go through the link

rachit_28 · November 17, 2012, 9:56am

Find the coefficient of x^27 in (x^2 + 2x)^15.

surajsrivastav · November 17, 2012, 9:57am

Mukesh, Suresh, and Diensh travel form Delhi to Mathura to attend JanmasthmiUtsav. They have a bike which can carry only two rides at a time as per traffic rules. Bike can be driven only by Mukesh. Mathura is 300km form Delhi. All of them can walk at 15km/hr. All of them start their journey from Delhi simultaneously and are required to reach Mathura at the same time. If the speed of bike is 60km/hr then what is the shortest possible time in which all there can each Mathura at the same time.

estallar12 · November 17, 2012, 9:57am

@chillfactor said:
Its not possible to explain it here (atleast I can't do it), check the link. Actually no need to do all these things, even if a question is asked on the same logic, then the numbers will be smaller which can counted manually. In case you wanna learn I would say that you should go through the link

😲 😲 😲 :O

Sorry for Spamming...But then Chill Saar, you're finally here after such a long time..!!

\\________________________O____

Aap the kidhar Saar itne din..?? Darshan toh diya karo na !! :splat:

@chillfactor Saar- Kidhar ho abhi ? Espain se aaye kya ? Swadesh kab aaoge phir se ?

scarecrow28 · November 17, 2012, 9:58am

@rachit_28 said:
Find the coefficient of x^27 in (x^2 + 2x)^15.

3640?

saurav5517 · November 17, 2012, 10:00am

@rachit_28 said:
Find the coefficient of x^27 in (x^2 + 2x)^15.

420?

deedeedudu · November 17, 2012, 10:00am

@rachit_28 said:
Find the coefficient of x^27 in (x^2 + 2x)^15.

3640
PS: @chillfactor sir \\____O/_

akansh_1 · November 17, 2012, 10:00am

@rachit_28 said:
Find the coefficient of x^27 in (x^2 + 2x)^15.

Coefficient of x^27 in x^15(x+2)^15 = 15C1 * 2^12

surajsrivastav · November 17, 2012, 10:02am

@rachit_28 said:
Find the coefficient of x^27 in (x^2 + 2x)^15.

3640..

x^15(x+2)^15... coeff of x^12 in (x+2)^15