Official Quant thread for CAT 2013

MBA CAT 2022
1701
@rachit_28 said:
In how many ways can 32 different books be divided equally amongst 1.4 BoysI approached like this: 32C8*4*24C8*3*16C8*2 sahi hai ?PS: aaj to mein aapke peeche hi pad gaya
I would do it like this:
32! / ( 8!8!8!8!4!) = Distinct groups

Now distribute them in 4! boys => Ans = 32!/(8!8!8!8!) ?
1702
@farziPandit said:
Am i also ordering the cards instead of selecting if i'm going with 52 * 36 * 22 * 10 instead of 13 * 12 * 11 *10 ???@Brooklyn@rubikmath thoda prakash daale , still not clear which one to go for!!!
13*12*11*10
1703
@rachit_28 said:
In how many ways can 32 different books be divided equally amongst 1.4 BoysI approached like this: 32C8*4*24C8*3*16C8*2 sahi hai ?PS: aaj to mein aapke peeche hi pad gaya
yaar 4! multiply nai hoga
32c8*24c8*16c8*8c8
=>32!/(24!*8!)*24!/(16!*8!)*16!/(8!*8!)*1
=>32!/(8!^4)
1704
@krum said:
yaar 4! multiply nai hoga32c8*24c8*16c8*8c8=>32!/(24!*8!)*24!/(16!*8!)*16!/(8!*8!)*1=>32!/(8!^4)
y not 4! ?? boys are different !!
1705
@Brooklyn said:
13*12*11*10
is there arrangement of cards apart from selecting also if we are going for 52*36*22*10 ???
1706
@farziPandit said:
Am i also ordering the cards instead of selecting if i'm going with 52 * 36 * 22 * 10 instead of 13 * 12 * 11 *10 ???@Brooklyn@rubikmath thoda prakash daale , still not clear which one to go for!!!
yaar answer this "number of ways of selecting 4 alphabets"?
is it 26c4 or 26*25*24*23?
1707
@ani4588 said:
A medical clinic tests blood for certain disease from which approximately one person in a hundred suffers. People come to the clinic in group of 50. The operator of the clinic wonders whether he can increase the efficiency of the testing procedure by conducting pooled tests. In the pooled test, the operator would pool the 50 blood samples and test them altogether. If the pooled test was negative, he could pronounce the whole group healthy. If not, he could then test each person창€ℒs blood individually. The expected number of tests the operator will have to perform if he pools the blood samples are: (A) 47 (B) 25 (C) 21 (D) None of the aboveapproach plz??
What a question!!!!

My take is 20.6 (approx 21)

P(One person being unhealthy) = 1/100
Now, in a group of 50 ---- 0 or 1 or 2 or 3 or .. 50 can be unhealthy.
Corresponding probabilities are:
0 unhealthy => 50C0 * (99/100)^50
1 unhealthy => 50C1 *(1/100) * (99/100)^49
2 unhealthy => 50C2 *(1/100)^2 * (99/100)^48
...
...
50 unhealthy => 50C50 *(1/100)^50

Except first case, we get 50 tests in all other cases as he goes for each individual's tests in all other cases.

So, P(1 test needed) = (99/100)^50 => 0.60
Used a calculator to do this..had no other option

=> 6 groups out of 10 will need 1 test each (6/10 = 0.6)
=> 4 groups will need 50 tests each (remaining 4 groups)

=> Total tests = 6 + 4*50 = 206
Total groups = 10

=> Avg. number of tests needed per group = 206/10 = 20.6

@krum Is there a better way to solve this?
1708
@krum pehle 8 books choose kar li, now we have 4 choices know, for next 8, 3 choices, and so on, isliye multiply kiya 😞 thoda aur prakash daalo πŸ˜ƒ
1709
@Brooklyn said:
y not 4! ?? boys are different !!
yaar 32c8 means all the possible combinations of 8 among 32
if we multiply 4! means we are considering order in which books are distributed

think about this question and this 1
"In how many ways can 32 different books be divided equally among 4 shelves"
here we will multiply 4! because order of shelf matters
@rachit_28
1710
@soumitrabengeri said:
What a question!!!! My take is 20.6 (approx 21)P(One person being unhealthy) = 1/100Now, in a group of 50 ---- 0 or 1 or 2 or 3 or .. 50 can be unhealthy.Corresponding probabilities are:0 unhealthy => 50C0 * (99/100)^501 unhealthy => 50C1 *(1/100) * (99/100)^49 2 unhealthy => 50C2 *(1/100)^2 * (99/100)^48...... 50 unhealthy => 50C50 *(1/100)^50Except first case, we get 50 tests in all other cases as he goes for each individual's tests in all other cases.So, P(1 test needed) = (99/100)^50 => 0.60 Used a calculator to do this..had no other option=> 6 groups out of 10 will need 1 test each (6/10 = 0.6)=> 4 groups will need 50 tests each (remaining 4 groups)=> Total tests = 6 + 4*50 = 206Total groups = 10=> Avg. number of tests needed per group = 206/10 = 20.6@krum Is there a better way to solve this?
i did the same, techsurge posted it few days back, again an IIFT question
what is wrong with IIFT, its like they want people to mess it up
1711
@krum said:
yaar answer this "number of ways of selecting 4 alphabets"?is it 26c4 or 26*25*24*23?
okay got it!!!
1712
@krum shelves waali baat to samajh mein aa gayi, lekin ye samajh mein nhi aaya, 32 mein se first 8 books select karne ke baad hamare pass 4 choices hogi naa, ki kaunse boy ko de ?
@soumitrabengeri
1713
@rachit_28 said:
@krum shelves waali baat to samajh mein aa gayi, lekin ye samajh mein nhi aaya, 32 mein se first 8 books select karne ke baad hamare pass 4 choices hogi naa, ki kaunse boy ko de ?
i feel u, lets take an example with 4 books to be equally distributed among 2 boys.

books - a,b,c,d

4c2 means - (a,b),(a,c),(a,d),(b,c)(c,d)(c,d)

so if i write 4c2*2c2=4!/(2!*2!) it means first boy already got all possible combinations of book, same for second, can u think of any 1 case where second boy doesn't get a particular pair of book?

now if i multiply by 2*1=2!, it means i'm considering order in which books are given

however if it were a shelf, the books can be arranged among themselves so 4c2*2c2*2!*2!
1714
@rachit_28 said:
@krum shelves waali baat to samajh mein aa gayi, lekin ye samajh mein nhi aaya, 32 mein se first 8 books select karne ke baad hamare pass 4 choices hogi naa, ki kaunse boy ko de ?@soumitrabengeri
I followed the question till the books were to be distributed among boys..ye beechmese shelves kahase aa gaye?
@krum ka solution correct hai na? Even i would have approached the problem in the same way
1715
A square field of size 72 β€”72 is to be covered by rectangular tiles (with integral edges) with length to breadth ratio is 3 : 2. What is the difference between minimum and maximum number of tiles used?
(A) 864 (B) 210 (C) 426 (D) 860 (E) None of these
1716

Data sufficiency:

What is a two digit number?
I. Sum of the digits of the number is 8.
II. Difference of the digits of the number is 2.

1717
@catter2011 said:
A square field of size 72 β€”72 is to be covered by rectangular tiles (with integral edges) with length to breadth ratio is 3 : 2. What is the difference between minimum and maximum number of tiles used?(A) 864 (B) 210 (C) 426 (D) 860 (E) None of these
none of these
max when tile is of 3x2 so tile required = 24 x36 = 864
min when tie is of 36x24 so tile required = 3 x2 = 6
858
1718
@catter2011 said:
Data sufficiency: What is a two digit number?I. Sum of the digits of the number is 8.II. Difference of the digits of the number is 2.
I
17 , 71 , 26 , 62..cant say

II
24 42 64 46... cant say

combining
53 , 35 cant say
1719
@catter2011 said:
Data sufficiency: What is a two digit number?I. Sum of the digits of the number is 8.II. Difference of the digits of the number is 2.
question cannot be answered using both statements together
1720
@catter2011 said:
Data sufficiency: What is a two digit number?I. Sum of the digits of the number is 8.II. Difference of the digits of the number is 2.
35 or 53 ....CBD