GMAT Data Sufficiency Discussions

Hi Naveen,

I posted the same solution for one more query below and still have the same doubt ...

1. If the operation # is one of the four operations +, - , * (multiply) and / (divide), is (6 # 2) # 4 = 6 # (2 # 4)?
(1) 3 # 2 > 3
(2) 3 # 1 = 3

1) e
i) Gives two choices; 3+2>3 & 3*2>3; Hence insufficient
ii) Gives two choices; 3*1=3 & 3/1=3 ; Hence insufficient.
I am a bit confused with this one. Mathematically the equation given (6 # 2) # 4 = 6 # (2 # 4) is right for whatever operation we may assign to #. However it is not true for option i) & ii), hence E)

2..Is z equal to Median of the three positive integers x,yand z.
A)x2 b)
a) x
If x=5, y=1, z=6; Median = x
If x=1, y=2, z=3; Median =y
Hence insufficient
b) y=z; If y=z then irrespective of value of x, median has to be y or z
if x=1, y=5, z=5; Median = 5
if x=10 y=5, z=5; Median = 5
Hence B sufficient
Thanks



Ans for 1st question is A............I din get the explanation from newhere..
nssaini Says
Ans for 1st question is A............I din get the explanation from newhere..



from the first statement you get that either of + or * is the operator. but both operators tell that the two expressions compared are equal. So A alone can give the answer. But / doesnt hold since it gets the first priority in terms of opertors present. And hence statement two is insufficient to gie answer.
I think you have miread the questions, instead of ascertaining the operator you were just required to check if the equality holds.

Hi guys,
I have attached the screenshot of the problem (& its explanation) I solved in the kaplan test. Please go through it.


My doubt is: In the question they havent mentioned, whether Peter's best time in swimming was for 1500m or 2000m or whatever.
By chance in this case, from the statements we can infer that the present time is between 20 mins & 22 mins. So answer is E as we cant say for sure.

But I feel even if we could prove that the timing is less than 21 mins, the answer should still be E, as in the question they havent mentioned the distance at all.

What say?


....
Each of the students in a certain class received a single grade P, F or I. What percent of students in the class were females?
(1) Of those who received a P, 40% were females.
(2) Of those who received either an F or I, 80% were males.

6) E (Guess)
Cannot solve this one.

Good work Sailor !!

Let p students receive grade P and let the remaining students o receive grade F or I.
Thus,total students = p+o.
To find (Females/p+o) x 100 ?
St 1: Females with P = 0.4p . But No information about females with F or I. Insufficient
St 2: Females with F or I = 0.2o . But No information about females with P. Insufficient

Combining the 2:
Percentage of females = (0.4p + 0.2o)/(p+o) x 100
Not possible to find. -> Answer E
Plz post the explanations as well.

1.If the operation * is one of the four Arithmatic operation addition,Subtraction,Multiplication and division.Is (6*2)*4=6*(2*4)
A)3*2>3
B)3*1=3

I am not sure about operation substitution. Check there is one post dealing with this problem.


2..Is z equal to Median of the three positive integers x,yand z.
A)x


A. x=4,y=7,z=8 -> z not a median
x=4,z=7,y=8 -> z is a median
Insufficient

B. x=4,y=7,z=7 -> Median is 7. so z is a median
y=4,z=4,x=7 -> Median is 4. so z is a median
Sufficient
Answer B

Hi,
I need to start prep for Data Sufficiency.
Can sb plz suggest me where to start with.
Also, i need OG 11 - DS, can sb help me on this one.

Thanks in advance.

Hey guys,
I observed that like me, most of the guys in this forum are somewhat confused with operation substitution problems.

Found one good problem in Kaplan, which may improve our understanding little bit.

One of the Q from GPrep on DS..


If a and b are nonzero on the number line, is 0 between a and b ?
1. The distance between 0 and a is greater than the distance between 0 and b.
2. The sum of the distance between 0 and a and between 0 and b is greater than the distance between 0 and the sum a+b ?

guys plz help me out with this one...

Is y an integer?
(1) y3 is an integer
(2) 3y is an integer

Hi,
Please help me out with this DS question. Please provide explanation for the answer.

In the xy-plane, does the line with equation y=3x+2 contain the point (r,s) ?
1. (3r+2-s) (4r+9-s) = 0
2. (4r-6-s) ( 3r+2-3) = 0

Hi,
Another DS question for which I need some explanations.
If y is an integer and y = x + x, is y=0?
1. x2. y

Hi,
Please help me out with this DS question. Please provide explanation for the answer.

In the xy-plane, does the line with equation y=3x+2 contain the point (r,s) ?
1. (3r+2-s) (4r+9-s) = 0
2. (4r-6-s) ( 3r+2-3) = 0


For the point (r,s) to lie on y = 3x+2 it must satisfy the equation i.e. s= 3r+2

From 1st statement we get s = 3r+2 or 4r+9
From 2nd statement we get s= 4r-6 or 3r+2 ( i guess there was a typo in the 2nd statement u have poted)

And using both these conditions we can get s= 3r+2
So, the ans should be C

Hope that explains.

Cheers,
Akx.
Hi,
Another DS question for which I need some explanations.
If y is an integer and y = x + x, is y=0?
1. x2. y

This can be solved using either of the two statements i think.
Is that correct??
Ans is C. Am i correct?
From (1) we can infer y and z have same sign. Similarly from (2) x and y have same signs. So combining both x, y, z have same sign. So x(y+z) is greater than 0.


Hi explaination is correct. But answer is wrong. x,y z all have same sign. if all are -ve xyz 0 . so anwer is E:)
Are at least 10% of the people in Country X who are 65 years old or older employed?

1) In Country X, 11.3% of the population is 65 years old or older.

2) In Country X, of the population 65 years old or older, 20% of the men and 10% of the women are employed. x


Answer is C

11.3%* (20%)
Here question is 10% of total population
For all the triangles to be equilateral, all the sides need to be of equal length since the triangles will have common sides. Hence we can answer it using (1) alone.

However, (2) does not ensure that the triangles will be equilateral. The three segments can be any three diameters of a circle and can be drawn in such a way that the sides are not equal.

Hence answer is (1) alone.


Hey Answer is D.
Only in Regular Hexagon all sides are equal, and the 3 segmenst are equal. In regular hexagon all these triangles are Equilateral triangles

Need help on this DS question from OG11 ( # 40)

What is the Value of Integer N
1) n(n+1) = 6
2) 2 ^ 2n = 16

My answer would be E. because 16 can also be (-2) ^ 4
So you really cannot compare the base ,but the answer in OG 11 is B :-(( ..
Am i missing something..please help..

Need help on this DS question from OG11 ( # 40)

What is the Value of Integer N
1) n(n+1) = 6
2) 2 ^ 2n = 16

My answer would be E. because 16 can also be (-2) ^ 4
So you really cannot compare the base ,but the answer in OG 11 is B :-(( ..
Am i missing something..please help..


Hi
You cannot change the question. 2^ 2n=16 .You can give value to n only are theer 2 values of n which can give value of 16.. Answer is no. There is only one value i.e n=2.So anwer is B.. the 2 at base cannot be changed by us.

sriram,
thanks for ur response.. i was just trying to redefine 16..with possible options .but you are right.. need to factor the constraints on both sides.. ..i got it now..dont know why it seemed strange yesterday.....see ya

Q1) If x and y are positive integers and x is a multiple of y, is y = 2?
(1) y 1
(2) x + 2 is a multiple of y.


Q2) If x and y are integers between 10 and 99, inclusive, is ((x-y)/9) an integer?
(1) x and y have the same two digits, but in reverse order.
(2) The tens digit of x is 2 more than the units digit, and the tens digit of y is 2 less than the units digit.