Official Quant thread for CAT 2013

@pavimai said:
s(n) is defined as number of integers (1,2,...n)that are relatively prime to n .if n is product of two prime numbers,whose sum is 40 and s(n)=280 then n are??
Is it 319?
@Calvin4ever said:
Find the least possible value of (a+b+c)(1/a + 1/b + 1/c)
If i put a=b=c as 1/100, we have a+b+c as 3/100 n 1/a + 1/b + 1/c = 300..Hence, It will be 1/10,000...Coz there are no conditions mentioned abt the nature of a, b n c..

N similarly it can be seen that the expression cannot have a minima.. 9 kaise ho sakta hai minima..i can't understand .
@prateek987 said:
@Joey_Sharma joey..tum ek behad subtle galti kar rahe ho...question ki shuru ki do lines dhyan se padho..
yeah!! i got it now. i considered 2112 as the actual data for this year. thanks!
@IIMAIM said:
Since least value is asked making c as -1 makes-3*-3=9
Point taken, but try a = -100, b = -100, c = +1 and see what the value comes?

regards
scrabbler

@pyashraj said:
If i put a=b=c as 1/100, we have a+b+c as 3/100 n 1/a + 1/b + 1/c = 300..Hence, It will be 1/10,000...Coz there are no conditions mentioned abt the nature of a, b n c..N similarly it can be seen that the expression cannot have a minima.. 9 kaise ho sakta hai minima..i can't understand .
Question setter forgot to specify "positive integers" so we are all having fun at the expense of the question :D

regards
scrabbler

@scrabbler

Yeah..Mera paas Valentine toh nahi hai..Isliye Question ke saath flirt kar raha hun..

Hwever, Even if the positive Integers condition is implied..Answer cannot be 9..1 hoga shayad then.. at a=b=c = 1...It will be 1 then..
@scrabbler said:
Question setter forgot to specify "positive integers" so we are all having fun at the expense of the question regardsscrabbler
hmm -infinity
@pavimai said:
s(n) is defined as number of integers (1,2,...n)that are relatively prime to n .if n is product of two prime numbers,whose sum is 40 and s(n)=280 then n are??
n=11*29
319
@Calvin4ever said:
Find the least possible value of (a+b+c)(1/a + 1/b + 1/c)
AM>HM
(a+b+c)/3>3/(1/a+1/b+1/c)

(a+b+c)(1/a+1/b+1/c)>9

minmum value is 9
what should be the values of a and b such that 30a0b03 is divisible by 13?
A 50 digit number has all 7 s .find the remainder when the number is divided by 74
@gnehagarg said:
AM>HM(a+b+c)/3>3/(1/a+1/b+1/c)(a+b+c)(1/a+1/b+1/c)>9minmum value is 9
in the question it is never stated a,b,c are positive if they are positive it is 9
-infinity otherwise

a= 8 ,b=1ďťż

or 2 ,3 or
5,2
@pavimai said:
A 50 digit number has all 7 s .find the remainder when the number is divided by 74
7/74=7 , 77/74=3, 777/74=37, 7777/37=7
repeating after 3 cycles so 50/3=2
so 3
@IIMAIM said:
77/74=3,777/74=37,7777/37=7,77777/7=3repeating after 3 cycles so 50/3=2so 37
options
3
13
23
33

@pavimai said:
A 50 digit number has all 7 s .find the remainder when the number is divided by 74
37 hoga kya?
@pavimai said:
options 3132333
@pavimai 3 as we have to start from 7/74=7 (i missed it)
@joyjitpal said:
37 hoga kya?
no 3
@IIMAIM said:
no 3
oh mistake

Maximum number of square possible that can be constructed using 31 pencils of equal length on the table? PLEASE explain the method