Official Quant thread for CAT 2013

MBA CAT 2024
12301
@anilapex said:
Find the greatest number, which will divide 215, 167 & 135 so as to leave the same remainder in each case?a) 64b) 32c) 24d) 16Do share the approach.
For such questions use the following method
Take the diff of any 2 sets of numbers from the 3 numbers
Suppose we consider 215,167 and 167,135
215-167 = 48
167-135 = 32
Then we take the HCF of these 2 numbers and that will give us the answer
HCF (48,32) = 16
So the answer is 16
12302
@anilapex said:
Find the greatest number, which will divide 215, 167 & 135 so as to leave the same remainder in each case?a) 64b) 32c) 24d) 16Do share the approach.
d) 16...
12303
@anilapex said:
Find the greatest number, which will divide 215, 167 & 135 so as to leave the same remainder in each case?a) 64b) 32c) 24d) 16Do share the approach.
16...go through options
12304
@Crysis said:
And considering they are black and white, they can switch places too so 1596*2 = 3192....
bhai I have done it like this
ways of no attacks=total ways- ways of attacks
=(64*63) -{ 36*8 + 24*5 + 4*3}=3612...... (as usual I dont have the OA for this)
12305

Question. If a man starts from a point a and take 8 steps. each in the direction of either north, south, east, west, north-east, northwest, southeast, southwest. What is the probability that the path traced by him forms a regular polygon?

12306
@DarkHorse25 said:
yes but u ve to consider 215-135=80 .there are cases skipping the third deduction may lead you to wrong answer
Even if we do consider 80..still HCF (80,48) = 16
HCF (80,32) = 16
12307
@DarkHorse25 said:
yes but u ve to consider 215-135=80 .there are cases skipping the third deduction may lead you to wrong answer
No it will not
take the HCF of (32,48,80)=16 {and you can conclude the value 16 by taking HCF of any two values from the triplet (32,48,80)}
12308
@soumitrabengeri said:
Even if we do consider 80..still HCF (80,48) = 16HCF (80,32) = 16
yes here luckily 80 is multiple of 16 .. i was mistaken in same type of ques .. didnt take third difference .. and marked the wrong ans...
12309
@anantn said:
Question. If a man starts from a point a and take 8 steps. each in the direction of either north, south, east, west, north-east, northwest, southeast, southwest. What is the probability that the path traced by him forms a regular polygon?
1/7!?
12310
@anilapex said:
Find the greatest number, which will divide 215, 167 & 135 so as to leave the same remainder in each case?a) 64b) 32c) 24d) 16Do share the approach.
in such questions where the remainder comes out to be the same....
find the HCF of the difference between the given numbers..and that will be the required answer....

say the numbers be A+r, B+r, C+r

so on calculating the difference u will be able to eliminate the remainder part that is common to all the three numbers...

the above question is reduced to find the HCF of 32, 48, 80.

now solve and u will get 16 as the answer..
:)
12311
@anantn said:
Question. If a man starts from a point a and take 8 steps. each in the direction of either north, south, east, west, north-east, northwest, southeast, southwest. What is the probability that the path traced by him forms a regular polygon?
i will also go with 8/8! = 1/7!...correct....?
12312
@anantn said:
Question. If a man starts from a point a and take 8 steps. each in the direction of either north, south, east, west, north-east, northwest, southeast, southwest. What is the probability that the path traced by him forms a regular polygon?
8/8!?
12313

@shadowwarrior
@19rsb
I dont have OA for this..but i got a completely different answer...can you guys explain your approach? why is 8! in the denominator? shouldnt it be 8^8, since at each step he has 8 options
12314
@DarkHorse25 said:
yes it can.. in ur prev post u didnt consider 80 .. u considered only 32 and 48 .. which is not correct..
I dont think it can go wrong..could you please give an example where the 3rd difference was necessary to determine the HCF?
12315
@anantn said:
@shadowwarrior@19rsbI dont have OA for this..but i got a completely different answer...can you guys explain your approach? why is 8! in the denominator? shouldnt it be 8^8, since at each step he has 8 options.


I agree with you.. it should be 8/8^8
12316
@anantn said:
@shadowwarrior@19rsbI dont have OA for this..but i got a completely different answer...can you guys explain your approach? why is 8! in the denominator? shouldnt it be 8^8, since at each step he has 8 options
after he used east step, he can't reuse it no.....thats what i understood from the question...so no 8^8 but 8!
12317
@anantn said:
@shadowwarrior@19rsbI dont have OA for this..but i got a completely different answer...can you guys explain your approach? why is 8! in the denominator? shouldnt it be 8^8, since at each step he has 8 options
"each in the direction of either north, south, east, west, north-east, northwest, southeast, southwest"........YAA I have missed the word "either" while reading......so I think you may be correct
12318
@19rsb
in addition to that how did you come up with 8 cases, can you elaborate on that?
12319

Question 2:In a class, of 10 students, any 5 students are selected for student council, each of the students can choose to vote for the president of council, and can vote for any of the other 4 students, or with old his/her vote. The student with the most number of votes becomes the president. What is the probability that the number of votes won by the president is a perfect square?

Guys, please share entire approach along with the answer. :)

12320

No OA for the above, i solved and got answer as 1/(5^4). not 100% sure though...