GMAT Data Sufficiency Discussions

Thanks for pointing out my mistake... yes i cannot divide it by xy...

But are you suggesting that x2 and y2 are different variables? If yes then the question does not make sense at all...

@nuttyvaru: Can you throw some light on this?


well.. I am convinced that I was right to begin with and the answer has to be option E only.. but for ur help I have updated the original question..

I believe I copied and pasted it, and that what made the superscript look like a subscript in here.. and I didnt notice that... anyway.. hope this helps clarify things for you.. πŸ˜‰
Coordinate geometry sux man...


In the
xy-plane, the line with equation ax + by + c = 0, where abc is not equal to 0, has slope 2/3. What is the value of b?
(1)

a = 4
(2)
c = 6


ax+by=6
x/(6/a)+y/(6/b)=1

slope of this equation is=-(6/b)/(6/a)=-b/a=2/3

So nothing can be said abt a or b.

Can anybody help me in solving this DS question:

Is sqrt ((x-3)^2) = 3 - x?
A) x not equal to 3
B) -x x > 0

I know the answer but no clue?

I feel sqrt can give value of x-3 or 3-x
and for x-3 = 3-x gives x = 3
so x not equal to 3 rules out that but if sqrt value is 3-x then its valid for all.

Can anybody help me in solving this DS question:

Is sqrt ((x-3)^2) = 3 - x?
A) x not equal to 3
B) -x x| > 0

I know the answer but no clue?

I feel sqrt can give value of x-3 or 3-x
and for x-3 = 3-x gives x = 3
so x not equal to 3 rules out that but if sqrt value is 3-x then its valid for all.


Hey buddy ...Ans is B ..

statement in bold is incorrect ..
square root of a positive number is always non negative..

(x-3)^2 is positive and root of is non negative only...
Hence, root of is x-3 and not just x-3 or 3-x...

so, the question asked rephrases to , is x-3 = 3-x ??

for this to hold true, 3-x > 0 i.e x
So, finally question boils down to is x

St 1 : x is not equal to 3 ...this does not tell us if x is less than 3 ...not sufficient ..

St 2 : -x x >0...
|x is always positive, so -x should be positive or x should be negative ...i.e xHence always, x
Hence, Ans B

square root of a positive number is always non negative..

(x-3)^2 is positive and root of is non negative only...
Hence, root of is x-3| and not just x-3 or 3-x...


Hi,

Can you explain me how can "square root of a positive number be always non negative"... sqrt(x) takes positive and negative values. I think you meant something else here.

Also, |x-3 is equivallent to saying +/-(x-3) which would be either (x-3) or -(x-3) that is 3-x...
this is easy.. ;)

If positive integer x is a multiple of 6 and positive integer y is a multiple of 14, is xy a multiple of 105?
(1) x is a multiple of 9.
(2) y is a multiple of 25.

1 is not sufficient to answer the question.
From 2, we can conclude that y is a multiple of 5. So xy is multiple of 3, 7 and 5 and hence 105

So the answer is B
Can anybody help me in solving this DS question:

Is sqrt ((x-3)^2) = 3 - x?
A) x not equal to 3
B) -x x > 0

I know the answer but no clue?

I feel sqrt can give value of x-3 or 3-x
and for x-3 = 3-x gives x = 3
so x not equal to 3 rules out that but if sqrt value is 3-x then its valid for all.

Sqrt ((x-3)^2) = 3- x only if x -3

From A, we cannot say if x
From B, x
If x

So B is sufficient to answer the question.
Hence choice B.
Hi,

Can you explain me how can "square root of a positive number be always non negative"... sqrt(x) takes positive and negative values. I think you meant something else here.

Also, x-3| is equivallent to saying +/-(x-3) which would be either (x-3) or -(x-3) that is 3-x...


Hey ...conventionally square root of positive no takes non negative values only ..its the same way as we say 0! =1

eg root 9 is only +3 and not -3 ...
And By x-3 i meant the positive absolute value of diff between x and 3 ...it is not the same as (x-3) or (3-x), infact one of the realtion would hold true depending on value of x, but not both

For instance if xand if x>3 then sqrt ((x-3)^2) is x-3 ,

So to sum up , sqrt ((x-3)^2) = |x-3...

can post up few more links regarding sign convention of roots if u need..
ax+by=6
x/(6/a)+y/(6/b)=1

slope of this equation is=-(6/b)/(6/a)=-b/a=2/3

So nothing can be said abt a or b.



hey slope here is (-b/a)
-b/a=2/3

so -b=2k where k is constant
a= 3k

from
1. a=4
substitue we get k=4/3
substitue for b, =-8/3

can ans by 1.
2. cannot ans using option

so ans is A.
1 alone can ans.
hey slope here is (-b/a)
-b/a=2/3

so -b=2k where k is constant
a= 3k

from
1. a=4
substitue we get k=4/3
substitue for b, =-8/3

can ans by 1.
2. cannot ans using option

so ans is A.
1 alone can ans.


Hey ..Ans is indeed A .
However small slip at ur end ..
Slope is -a/b
hey slope here is (-b/a)
-b/a=2/3

so -b=2k where k is constant
a= 3k

from
1. a=4
substitue we get k=4/3
substitue for b, =-8/3

can ans by 1.
2. cannot ans using option

so ans is A.
1 alone can ans.


Thats implicity I have said

There are approximately 2.2 pounds in one kilogram. To the nearest eighteenth, how many eighteenths of a kilogram are in one pound?


1. 7
2. 8
3. 9
4. 39
5. 40

I am not sure what this problem means even..please help.

There are approximately 2.2 pounds in one kilogram. To the nearest eighteenth, how many eighteenths of a kilogram are in one pound?


1. 7
2. 8
3. 9
4. 39
5. 40

I am not sure what this problem means even..please help.


he he ..this is only tying to play with words ..
ok...there would be 18 eighteenths in 1 kilogram ( simply speaking its like 2 halves, 4 quarters etc)
i.e in other words 18 eighteenths of a kilogram in 2.2 pounds
so in 1 pound there would be 18/2.2 = 8
Is
xy > (x^2)(y^2)?
(1) 14(
x^2)= 3

(2) (
y^2)= 1
The OA got be confused!! Please share your thoughts!!




Consider 2) y=+1 or -1 so not sufficient.
consider 1) x^2= 3/14 and there is no info on y so not sufficient.

consider 1 and 2 so now we have x^2*y^2 but we dont know the signs

hence E

any way what's the OA?

Hi,
EighteenTHS of a KG means 1/18 of a KG...

Now i guess, its quite simple as
1 KG = 2.2 Pounds
So question is how many 1/18ths of 1 kg are there in 2.2 pounds?

18/2.2 = 8

Cheers,
Amit

Consider 2) y=+1 or -1 so not sufficient.
consider 1) x^2= 3/14 and there is no info on y so not sufficient.

consider 1 and 2 so now we have x^2*y^2 but we dont know the signs

hence E

any way what's the OA?

XY > X^2 * Y^2
XY (1-XY) > 0.

So either XY shall be positive and XY 1 then only the inequality holds...

Lets evaluate the arguments...

14 * X^2 > 3

X^2 > 3/14 => X > SQRT ( 3/14 ) ~=> X > 0.45
Alone not sufficient as no talk about the Y => A), D) are gone

2)-> Y^2 > 1 => Y>1

Putting both together, we have an answer..."Yes", XY > X^2*Y^2...

My answer is C)...OA Please...

Cheers,
Amit
XY > X^2 * Y^2
XY (1-XY) > 0.

So either XY shall be positive and XY 1 then only the inequality holds...

Lets evaluate the arguments...

14 * X^2 > 3

X^2 > 3/14 => X > SQRT ( 3/14 ) ~=> X > 0.45
Alone not sufficient as no talk about the Y => A), D) are gone

2)-> Y^2 > 1 => Y>1

Putting both together, we have an answer..."Yes", XY > X^2*Y^2...

My answer is C)...OA Please...

Cheers,
Amit




here y^2>1 so y can be -2 or 2 in both the cases y^2 is 4

so we cannot say y>1

Puys what say?
ax+by=6
x/(6/a)+y/(6/b)=1

slope of this equation is=-(6/b)/(6/a)=-b/a=2/3

So nothing can be said abt a or b.

A alone is suffcient
XY > X^2 * Y^2
XY (1-XY) > 0.

So either XY shall be positive and XY XY 1 then only the inequality holds...

Lets evaluate the arguments...

14 * X^2 > 3

X^2 > 3/14 => X > SQRT ( 3/14 ) ~=> X > 0.45
Alone not sufficient as no talk about the Y => A), D) are gone

2)-> Y^2 > 1 => Y>1

Putting both together, we have an answer..."Yes", XY > X^2*Y^2...

My answer is C)...OA Please...

Cheers,
Amit


buddy ..statements in bold are incorrect ..

xy can never simultaneously be lesser than zero and greater than 1 ..only your 1st argument has to hold true..

question says its x square =3/14 ...it has 2 poss roots ...+ve n -ve
even if u say x^2 >3/14 it does not imply x is greater than root 3/14 only ..

eg ..x^2> 25 it implies x>5 or x
similarly for statement 2 also

Detailed approaches have been discussed 2 pages back ...everybody concurs Ans is E ..
buddy ..statements in bold are incorrect ..

xy can never simultaneously be lesser than zero and greater than 1 ..only your 1st argument has to hold true..

question says its x square =3/14 ...it has 2 poss roots ...+ve n -ve
even if u say x^2 >3/14 it does not imply x is greater than root 3/14 only ..

eg ..x^2> 25 it implies x>5 or x
similarly for statement 2 also

Detailed approaches have been discussed 2 pages back ...everybody concurs Ans is E ..


First of all my sincire apologies for severely overlooking the subtle rule that:
a^2 > b^2 => A> B; A
Still, i've come up with following
X> SQRT (3/14) ; x Y > 1 ; Y
Now big Question is that by drawing the 4 possible combinations here on number line....overlapping area results that...
XY(1-XY) > 0.

then why not answer shall be C?