GMAT Data Sufficiency Discussions

MBA GMAT
2367
CLASS -> AVG AGE -> NO. OF STUDENTS

A -> 15-> 6

B -> 16 -> 12

Is the standard deviation of ages of students in class A greater than that of class B ?

1) The difference between ages of any two students in class A is always more than 1 yr.

2) No student in class B is more than 6 months older than any other student.

I got the answer by instinct but can someone post a solution ?
2368

Can anybody please help me in this?
If P is a set of integers and 3 is in P, is every positive multiple of 3 in P?
1) For any integer in P, the sum of 3 and that integer is also in P.

2) For any integer in P, that integer minus 3 is also in P.

Will post the answer after a few responses...

2369

Given P = {3,a,b,...etc}

Statement 1:
==========
For any integer in P , n+3 is also in P.So, 3 is an integer in P.So 6 should also be in P and such wise 9,12,15...are also in P.

So suff

Statement 2:
==========
For any integer in P, n-3 is also in P. Since 3 is in P,so 6,9,12....etc shud also be in P. So this statement is also suff.

I will go with option D.

-Deepak.

2370
Given P = {3,a,b,...etc}

Statement 1:
==========
For any integer in P , n+3 is also in P.So, 3 is an integer in P.So 6 should also be in P and such wise 9,12,15...are also in P.

So suff

Statement 2:
==========
For any integer in P, n-3 is also in P. Since 3 is in P,so 6,9,12....etc shud also be in P. So this statement is also suff.

I will go with option D.

-Deepak.

The answer is A..
I have got the logic now.
Actually, I was considering the statement as any number + 3(which is already there in the set).
It had to be considered as 3(which is there in the set P)+ 3..
And about the answer, it is A because in the second statement, it says that subtract 3 from that number. So, you will get negative multiples but the question is about the positive multiples.
Was really curious about this question. By the way, this is from Princeton Review Book, Maths Bin 3..
2371
The answer is A..
I have got the logic now.
Actually, I was considering the statement as any number + 3(which is already there in the set).
It had to be considered as 3(which is there in the set P)+ 3..
And about the answer, it is A because in the second statement, it says that subtract 3 from that number. So, you will get negative multiples but the question is about the positive multiples.
Was really curious about this question. By the way, this is from Princeton Review Book, Maths Bin 3..


Hey,
I'm not convinced with ans as A. Reg the second statement, since 3 is there 6 shud be ther and since 6 is ther, 9 will be ther.So all the positive multiples of 3 will be there in P including the negative multiples.So second statement alone is suff to ans the question.

wat do u say?

-Deepak.
2373
Given P = {3,a,b,...etc}

Statement 1:
==========
For any integer in P , n+3 is also in P.So, 3 is an integer in P.So 6 should also be in P and such wise 9,12,15...are also in P.

So suff

Statement 2:
==========
For any integer in P, n-3 is also in P. Since 3 is in P,so 6,9,12....etc shud also be in P. So this statement is also suff.

I will go with option D.

-Deepak.


It should be A
From second statement, {3,a,b...} ==> we can derive only one value 3-3=0.
I didn't get that how can we get 6 or 9 from second statement.
2374
Given P = {3,a,b,...etc}

Statement 1:
==========
For any integer in P , n+3 is also in P.So, 3 is an integer in P.So 6 should also be in P and such wise 9,12,15...are also in P.

So suff

Statement 2:
==========
For any integer in P, n-3 is also in P. Since 3 is in P,so 6,9,12....etc shud also be in P. So this statement is also suff.

I will go with option D.

-Deepak.


The word "Also" in S2 makes the difference in answers. While 3 is there in the set, we dont know what is P? S2 says " For any integer in P, that integer minus 3 is also in P." Also P is a set of integers not necessarily positive and question asks about positive multiples of 3. for example set P = {....-3,0,3,6} if P=6 but all positive multiples of 3 are not in the set. so S2 is insufficient.

but my question is no matter what value of P we take, all positive multiples will never be there in the set. So basically S2 says NO to the answer and its definite NO. So S2 should be sufficient... and answer should be D. what say?
2375

Hi Mission PGPX,i would like to make one clarification here.

S2 here you are assuming that it is a finite set which may not contain all positive multiples of 3(may be the highest value is limited by 99 or 999).But why cant the set may be an infinite set which contains all positive multiples of 3.I think here you can't say a definite 'No' as the answer.
The answer should be A.

2376
It should be A
From second statement, {3,a,b...} ==> we can derive only one value 3-3=0.
I didn't get that how can we get 6 or 9 from second statement.

As MissionPGPX pointed out, it just gives 3 - 3 = 0 value in the set P.
After that, all the definiite values it gives are 0-3= -3 , -3-6 = -9 and so on..
2377
The word "Also" in S2 makes the difference in answers. While 3 is there in the set, we dont know what is P? S2 says " For any integer in P, that integer minus 3 is also in P." Also P is a set of integers not necessarily positive and question asks about positive multiples of 3. for example set P = {....-3,0,3,6} if P=6 but all positive multiples of 3 are not in the set. so S2 is insufficient.

but my question is no matter what value of P we take, all positive multiples will never be there in the set. So basically S2 says NO to the answer and its definite NO. So S2 should be sufficient... and answer should be D. what say?

Statement 2 is not a definite NO because it doesnot say that "only" 3-3 = 0, 0-3 = -3 and so on values are there in the SET P.
It says "also", these values are there.
So, we don't know for sure whether the positive multiples of 3 are there.
Hope, that solves the doubt.
2378
Can anybody please help me in this?
If P is a set of integers and 3 is in P, is every positive multiple of 3 in P?
1) For any integer in P, the sum of 3 and that integer is also in P.

2) For any integer in P, that integer minus 3 is also in P.

Will post the answer after a few responses...



from 1 : We can definitely say that its an infinite set.
it goes like this:
...-2,-1,0,1,2,3,4,5,6,7,8,9...
The only confusion I see here is; How can we know if a certain value will be there? Coz of this ambiguity I would not rate this as a GMAT question.
2379

GMAT Prep Question:
In the xy-Plane does the equation y=3x+2 contaion (r,s):

A)(3r+2-s)(4r+9-s)=0
B)(4r-6-s)(3r+2-s)=0

OA C

2380
from 1 : We can definitely say that its an infinite set.
it goes like this:
...-2,-1,0,1,2,3,4,5,6,7,8,9...
The only confusion I see here is; How can we know if a certain value will be there? Coz of this ambiguity I would not rate this as a GMAT question.


statement 1 is alone sufficient to solve the problem, as it is given that 3 is already in the set P and every integer + 3 is also available in P then we can say that every multiple of 3 is present in P. like 3, 3+3=6,6+3=9 and so on....correct me if I'm wrong....
2381
GMAT Prep Question:
In the xy-Plane does the equation y=3x+2 contaion (r,s):

A)(3r+2-s)(4r+9-s)=0
B)(4r-6-s)(3r+2-s)=0

OA C


from A: either s=3r+2 or s=4r+9.(2 values hence not sufficient).
from B: either s=3r+2 or s=4r-6.(2 values hence not sufficient).
Combining : s=3r+2
2382
GMAT Prep Question:
In the xy-Plane does the equation y=3x+2 contaion (r,s):

A)(3r+2-s)(4r+9-s)=0
B)(4r-6-s)(3r+2-s)=0

OA C



Statement 1:
==========
Either 3r+2 = s or 4r+9 =s .Hence not sufficient

Statment 2:
=========
Either 3r+2 = s or 4r-6 = s.Hence not sufficient.

Combining both we get 3r+2 =s which definitely lies on the line.

Hence I will go with option C.

-Deepak.
2383
How many odd numbers are there between m and n?
(1) m n = 9
(2) 15m 15n = 135
2385
How many odd numbers are there between m and n?
(1) m n = 9
(2) 15m 15n = 135


Statement 1:
m-n = 9

m = 10 n = 1. So we will have 3 odd nos 3,5,7
m = 9 , n =0 .So we will have 4 odd nos 1,3,5,7.

So insuff.

Statement 2 : This is same as statement 1.So insuff.

combining also we cannot get the solution..

So I will pick option E

-Deepak.
2386
Statement 1:
m-n = 9

m = 10 n = 1. So we will have 3 odd nos 3,5,7
m = 9 , n =0 .So we will have 4 odd nos 1,3,5,7.

So insuff.

Statement 2 : This is same as statement 1.So insuff.

combining also we cannot get the solution..

So I will pick option E

-Deepak.


Good approach.
2387
1) If John traveled 9 miles on his unicycle, what was his speed in miles per hour?
(1) The unicycle has spokes that stretch the 23 inches from the center of the wheel to inner edge of the wheel.
(2) John pedals his unicycle at 19 revolutions per minute.
2) If w and k are distinct positive integers, do they have any common divisors other than 1 ?
(1) k w = 3w
(2) k and w are even.
3) If x and y are integers, is xy divisible by x2?
(1) x divides into y2 with no remainder.
(2) x is a prime.
4) Is ax > y?
(1) a = y = x
(2) a
5) Let (k + m) be a prime number where m and k are positive. How many divisors does k2 + mk have?
(1) k has 4 divisors.
(2) k = 6
2388
How many odd numbers are there between m and n?
(1) m n = 9
(2) 15m 15n = 135


Both Statements are not sufficient.
E.
"m and n are integers" is not mentioned.
So, it can be 4,5,6...depending upon the values...
Can you please post the OA...