Official Quant thread for CAT 2013

@Incognita123 said:
Wen v put a=b= -1 and c= 1....we get 1... No condition for a,b,c has been mentioned...
considering ur assumptions it is 1 as no condition specified on a,b,c
If a,b,c are positive numbers then it would be 9
@prateek987 said:
If attendance at a conference fell by 20 percent from last year, the attendance at the conference would have been 2112. If the attendance at the conference had instead risen by 25 percent, how many more people would have attended the conference this year?
Is it 1188?

@IIMAIM said:
considering ur assumptions it is 3 as no condition specified on a,b,cIf a,b,c are positive numbers then it would be 9
How is it 3 ?? Its 1 na? -1*-1= 1
@IIMAIM said:
considering ur assumptions it is 3 as no condition specified on a,b,cIf a,b,c are positive numbers then it would be 9
-1*-1=1... How did u get 3 ?
@Joey_Sharma wrong
@Incognita123 said:
How is it 3 ?? Its 1 na? -1*-1= 1
typo
@Joey_Sharma said:
Is it 1188?
3300 ?
@prateek987 said:
@Joey_Sharma wrong
3300 ?
@prateek987 said:
@Joey_Sharma wrong
Last year attendance was 2640 and to increase it by 25%, it should have been 2640+660=3300. But only 2112 people came. So to achieve 25% rise, 3300-2112=1188 more people should have come...This is what i got. Can u correct my data here?
@Joey_Sharma said:
Last year attendance was 2640 and to increase it by 25%, it should have been 2640+660=3300. But only 2112 people came. So to achieve 25% rise, 3300-2112=1188 more people should have come...This is what i got. Can u correct my data here?
Umm it shud b 3300-2640=660
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??
@Incognita123 said:
3300 ?
yeah!! i too got 3300 as this year attendance to satisfy 25% rise. But in the question, it is asking how many more would have attended this year.As only 2112 people came this year, so we need 1188 more people to reach the mark of 3300. So the answer should be 1188, not 3300. Do lemme know your thought.
@Joey_Sharma said:
yeah!! i too got 3300 as this year attendance to satisfy 25% rise. But in the question, it is asking how many more would have attended this year.As only 2112 people came this year, so we need 1188 more people to reach the mark of 3300. So the answer should be 1188, not 3300. Do lemme know your thought.
See..2112 is also an 'if' condition figure know... But d original figure is 2640... So d differnce with 3300 is 660
@Incognita123 said:
See..2112 is also an 'if' condition figure know... But d original figure is 2640... So d differnce with 3300 is 660
yeah!! my bad. i considered 2112 as this year actual data. it should be 660 then. thanks!!
@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??
23+17,3+37,11+29 satisfies sum to be 40
To find number of co primes for for a prime it is prime-1
so (11-1)(29-1)=280 satisfies ur product
391
@Incognita123 said:
Wen v put a=b= -1 and c= 1....we get 1... No condition for a,b,c has been mentioned...
Why not put c also as -1? :P

In fact let's make them all -100....kyun nahin?

regards
scrabbler

@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??
23+17,3+37,11+29 satisfies sum=40
as co primes for prime=prime-1
only (11-1)*(29-1) satisfies product=280
so N=11*29=319
@Joey_Sharma joey..tum ek behad subtle galti kar rahe ho...question ki shuru ki do lines dhyan se padho..
@scrabbler said:
Why not put c also as -1? In fact let's make them all -100....kyun nahin?regardsscrabbler
Since least value is asked making c as -1 makes
-3*-3=9

@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??
319?

My logic: If the two primes are p and q, i.e. n= pq, then to find s(n) we have to check numbers up to pq-1. Out of these p-1 will be divisible by q and q-1 will be divisible by p and rest will be co-prime to pq. Hence pq - 1 -(p-1) - (q-1) = pq - (p+q) +1 should be s(n). Now s(n) = 280 and (p+q) = 40 so pq - 40 + 1 = 280 gives us pq = 319 (a little checking will show us that this is 29*11)

regards
scrabbler