Official Quant thread for CAT 2013

@bullseyes said:
lets just say x = 12 x^2 = 144 no. of factors = 15 and according to formula the solutions are 29 rit? unfortunately this aint the answer
Then what is the answer ? I got 4N-2, where N = factors of x

So, for x = 12, it would turn out be 4*6 - 2 = 22 ?
@YouMadFellow said:
Then what is the answer ? I got 4N-2, where N = factors of xSo, for x = 12, it would turn out be 4*6 - 2 = 22 ?
the answer is = to no. factors of x^2 less then x
in this case, 7
@bullseyes said:
the answer is = to no. factors of x^2 less then x in this case, 7
Do you have a solution for this question ? If yes, do share
@chillfactor said:
Find all prime p for which (p^2 - 1)! is divisible by p^6 but not by p^7.
7
@YouMadFellow said:
Do you have a solution for this question ? If yes, do share
yes i do have but i would like to give few more time before publishing the answer.. dont want to ruin other's hard work.

A strictly increasing no. is one in which each digit exceeds the digit to its left. f.e. 1478
an increasing number is one in which each digit is not exceeded by digit to its left.
f.e 3445

how many inc. numbers are there below

a) one thousand
b) one million


(XAT kinda question)
@bullseyes said:
yes i do have but i would like to give few more time before publishing the answer.. dont want to ruin other's hard work. A strictly increasing no. is one in which each digit exceeds the digit to its left. f.e. 1478 how many strictly inc. numbers are there belowa) one thousandb) one million (XAT kinda question)

a)
2 digit - 9C2
3 digit - 9C3
=108

b)
similar process

Which is your other Question ?

@sujamait said:
a) 2 digit - 9C23 digit - 9C3=108b)similar process Which is your other Question ?
nope.

http://www.pagalguy.com/posts/4196330
@bullseyes said:
are single digits included ?

for that link..i guess chillfactor is rite.
@bullseyes said:
yes i do have but i would like to give few more time before publishing the answer.. dont want to ruin other's hard work.
Yup sure, no issues :)
@bullseyes said:
A strictly increasing no. is one in which each digit exceeds the digit to its left. f.e. 1478 how many strictly inc. numbers are there belowa) one thousandb) one million (XAT kinda question)
a) below 1000

10C3 (handles both 3 and 2 digit numbers) + 10C1 (single digit numbers) - 1 (zero) = 120 + 9 = 129 ?

b) below 1000000

Total = 10C6 + 10C4 + 10C2 = 45 + 210 + 210 = 465 ?
@bullseyes said:

A strictly increasing no. is one in which each digit exceeds the digit to its left. f.e. 1478 how many strictly inc. numbers are there belowa) one thousandb) one million (XAT kinda question)
a) C(9, 2) + C(9, 3) = C(10, 3) = 120

b) C(9, 2) + C(9, 3) + C(9, 4) + C(9, 5) + C(9, 6) = 456

(not sure if we have to include single digit numbers, is yes then 129 and 465)
@bullseyes said:
yes i do have but i would like to give few more time before publishing the answer.. dont want to ruin other's hard work.
for x = 12

1/z - 1/y = 1/12
(y + 12)(z - 12) = -144 = -1*144 = -2*72 = -3*48 = -4*36 = -6*24 = -8*18 = -9*16 = -12*12 = -16*9 = .... = -144*1
So, 15 solutions
and 15 solutions by swapping the negative and positive signs

But 12*-12 will give (0, 0) as solution, so we need to remove this case

Hence, 29 solutions
(7 will be the answer if question is asking for positive integral solutions)
@YouMadFellow said:
Yup sure, no issues a) below 100010C3 (handles both 3 and 2 digit numbers) + 10C1 (single digit numbers) - 1 (zero) = 120 + 9 = 129 ?b) below 1000000Total = 10C6 + 10C4 + 10C2 = 45 + 210 + 210 = 465 ?
@chillfactor said:
a) C(9, 2) + C(9, 3) = C(10, 3) = 120b) C(9, 2) + C(9, 3) + C(9, 4) + C(9, 5) + C(9, 6) = 456


i edited the question.. there was a little anomaly in previous one.
@YouMadFellow said:
Yup sure, no issues a) below 100010C3 (handles both 3 and 2 digit numbers) + 10C1 (single digit numbers) - 1 (zero) = 120 + 9 = 129 ?b) below 1000000Total = 10C6 + 10C4 + 10C2 = 45 + 210 + 210 = 465 ?
@chillfactor said:
a) C(9, 2) + C(9, 3) = C(10, 3) = 120b) C(9, 2) + C(9, 3) + C(9, 4) + C(9, 5) + C(9, 6) = 456


i edited the question.. there was a little anomaly in previous one.
@bullseyes said:
yes i do have but i would like to give few more time before publishing the answer.. dont want to ruin other's hard work. A strictly increasing no. is one in which each digit exceeds the digit to its left. f.e. 1478 an increasing number is one in which each digit is not exceeded by digit to its left.f.e 3445 how many inc. numbers are there belowa) one thousandb) one million (XAT kinda question)
a) C(12, 9)
b) C(15, 9)

It will be given by no of non-negative integral solutions of the eq
x0 + x1 + x2 + .... + x9 = n,
xr is no of times digit r appears and n is the no of digits in the largest number we can form

Edit:- we need to subtract 1 also, as 000 and 000000 is also counted
@bullseyes said:
yes i do have but i would like to give few more time before publishing the answer.. dont want to ruin other's hard work. A strictly increasing no. is one in which each digit exceeds the digit to its left. f.e. 1478 an increasing number is one in which each digit is not exceeded by digit to its left.f.e 3445 how many inc. numbers are there belowa) one thousandb) one million (XAT kinda question)

My take:
(a) 9C1 + 10C2 + 11C3 = 219
(b) 9C1 + 10C2 + 11C3 + 12C4 + 13C5 + 14C6 = Bhagwan jaane...

regards
scrabbler

@scrabbler said:
My take:(a) 9C1 + 10C2 + 11C3 = 219(b) 9C1 + 10C2 + 11C3 + 12C4 + 13C5 + 14C6 = Bhagwan jaane...regardsscrabbler
219 and 5004 is correct
@scrabbler said:
My take:(a) 9C1 + 10C2 + 11C3 = 219(b) 9C1 + 10C2 + 11C3 + 12C4 + 13C5 + 14C6 = Bhagwan jaane...regardsscrabbler
how???
@bullseyes said:
how???

@chillfactor's method is faster as it gives the answer with 1 calculation. I used a longer version of partitioning theory only.

Basically the idea is, suppose you want a 4 digit number. No digit can be greater than 9 and none less than 1. So you start from 1 and increment to 9, stopping at 4 points on the way (which are your 4 digits). Hence we need 5 increments totaling up to 8 units (an increment may be zero also since repeated digits are allowed). In other words we want to divide 8 units into 5 spaces or groups such that groups may be empty, which gives (8+4)C4 or 12C4. For 5 digits, 13C5 similarly, and so on...

Here we want up to 6 digits, so 9C1 + 10C2 + 11C3...till 14C6

But 8C0 + (9C1 + 10C2 + 11C3...till 14C6) = 15C6 and 8C0 is 1.

Hence it actually comes to the same 15C6 -1.

regards
scrabbler

@bullseyes said:
yes i do have but i would like to give few more time before publishing the answer.. dont want to ruin other's hard work.
Are you sure its integral solutions and not positive integral solutions ?

Let S = {2006, 2007, 2008,…….., 4012}. 'K' denotes the sum of the greatest odd divisor of each of the element of S. Find the value of 'K'.
@chillfactor said:
Are you sure its integral solutions and not positive integral solutions ?Let S = {2006, 2007, 2008,…….., 4012}. 'K' denotes the sum of the greatest odd divisor of each of the element of S. Find the value of 'K'.
it is positive integral but u can show for both
@chillfactor said:

Let S = {2006, 2007, 2008,…….., 4012}. 'K' denotes the sum of the greatest odd divisor of each of the element of S. Find the value of 'K'.
2^11 = 2048 (occurs only once in S)
2^10 = 1024 (need to considering all odd multiples only)
and so on..

K = 1 + (3) + (5 + 7) + (9 + 11 + 13 + 15) + ... + 4011

=> K = (1 + 4011)*(2006/2) = 4024036 ?