GMAT Data Sufficiency Discussions

MBA GMAT
735
in xy plane at what two points does the graph of y=(x+a)(x+b) intersects the x-axis.
1) a+b= -1
2) the graph intersects the y-axis at (0,-6)

the answer is c
Please anyone can explain me the reason why the answer is c.I will be pleased to see some helping me to solve the problem as i have tried this sum for 10 times and i cannot understand the question itself.


The answer is indeed C.
The question asks what are the zeros of the equation: y=(x+a)(x+b). Obviously y is 0 at x=-a, and -b. So the question is can we find the values of a and b.
stmt1: gives one equation, not sufficient.
stmt2: (0, -6) satisfies the equation y=(x+a)(x+b), so from here we get another relation in a and b as ab=-6.

So now we have 2 equations in 2 unknowns so it can be solved for a and b. So the answer is C.
736

Are x and y both positive?

(1) 2x - 2y = 1
(2) x/y > 1

737
Are x and y both positive?

(1) 2x - 2y = 1
(2) x/y > 1


from 1

x-y = 1/2

x=-1
y=-1.5

x=1
y=0.5

x=3/4
y=-1/4

inconclusive

x>y
x=1
y=-5

x=4
y=2

inconclusive

both together
x=1
y=o.5

x=3/4
y=-1/4

still inconclusive
Ans E
738

Hey.. i chose (E) as well.. but the OA is (C). Can someone plz help?!?!

This is one of the questions from GMAT Prep.


from 1

x-y = 1/2

x=-1
y=-1.5

x=1
y=0.5

x=3/4
y=-1/4

inconclusive

x>y
x=1
y=-5

x=4
y=2

inconclusive

both together
x=1
y=o.5

x=3/4
y=-1/4

still inconclusive
Ans E
739
Are x and y both positive?

(1) 2x - 2y = 1
(2) x/y > 1

My pick is C......

1. 2x - 2y = 1 ==> x-y=1/2
x=1 y=1/2 x-y=1/2
x=1/2 y=0 x-y=1/2 so not sufficient.....

2.x/y>1
not sufficient b/c x&y; can be both +ve or -ve.

combining we can eliminate counter example in st1 that x=1/2 & y=0 since x&y; should be both +ve or -ve. so C

correct me if i'm wrong.......
740

Another one from GMAT Prep:-

If x is a positive number less than 10, is z greater than the average (arithmetic mean) of x and 10?

1) On the number line, z is closer to 10 than it is to x.
2) z = 5x

741
from 1

x-y = 1/2

x=-1
y=-1.5

x=1
y=0.5

x=3/4
y=-1/4

inconclusive

x>y
x=1
y=-5

x=4
y=2

inconclusive

both together
x=1
y=o.5

x=3/4
y=-1/4

still inconclusive
Ans E

x>y
x=1
y=-5

mockingabird,
ur given example is not valid.......it doesnot give x/y>1
742
Another one from GMAT Prep:-

If x is a positive number less than 10, is z greater than the average (arithmetic mean) of x and 10?

1) On the number line, z is closer to 10 than it is to x.
2) z = 5x

My pick is A.

1. Mean will be midway b/w x & 10. it says that z closer to 10....that means z greater than mean.

2.No particular information helpful to solve the problem......
743
x>y
x=1
y=-5

mockingabird,
ur given example is not valid.......it does not give x/y>1


Yup overlooked it
Ans is C

Here is how it works
look at the two statements we infer that
both of them are positive or both of them are negative
and that x>y

Taking into consideration all these 3:
x- y = 1/2
-2+5/2 =1/2
but
x/y = 4/5 which violates that x/y>1

so they have to be both positive!!
744
Another one from GMAT Prep:-

If x is a positive number less than 10, is z greater than the average (arithmetic mean) of x and 10?

1) On the number line, z is closer to 10 than it is to x.
2) z = 5x


Ans is A

The closest you can get is x=7 z=9
17/2=8.5
The farthest range is x=1 z=9
11/2=5.5
consistent in the entire range.


The second one:
x=1
11/2= 5.5 5*x= 5
5.5>5

x=2
12/2=6 2*5=10

6
inconsistent
745

which two equation do we have
a+b= -1 and ab= -6 so how can we find a and b from this

746
which two equation do we have
a+b= -1 and ab= -6 so how can we find a and b from this


you need both of these equations to find a and b.
747
In the xy-plane, what is the slope of line l?
(1) Line l dose not intersect the line with equation y = 1 - x.
(2) Line l intersects the line with equation y = x - 1.
What is the value of the integer k?
(1) k + 3 > 0
(2) k^4 0
If x and y are positive, is x^3 > y?
(1) x > y
(2) x > y
748
In the xy-plane, what is the slope of line l?
(1) Line l dose not intersect the line with equation y = 1 - x.
(2) Line l intersects the line with equation y = x - 1.
What is the value of the integer k?
(1) k + 3 > 0
(2) k^4 0
If x and y are positive, is x^3 > y?
(1) x > y
(2) x > y


My take - A,B,D

1. stmt 1 - Line 'l' doesnt intersect y=1-x.. => the line l must be parallel to
y=1-x.. and hence line l's slope must be equal to line y=1-x's slope... ->
sufficient.
stmt 2 - Line 'l' intersects y=x-1. It can intersect at any angle...so slope cant be decided...

2. stmt 1 - K =3 >0 => k can be -2, -1, 0, 1,2,3,,........ not sufficeint
stmt 2 - K^4
3. both x & y are positive

stmt 1: x > y => x > y^2 => x^3 > Y^6,
and since ^6 > y => x^3 > y -- -sufficient
stmt 2: x > y => x^3 > y ^3...and since y^3 x^3 > y - sufficient
749
My take - A,B,D




OA's are A, B, E
750
My take - A,B,D

1. stmt 1 - Line 'l' doesnt intersect y=1-x.. => the line l must be parallel to
y=1-x.. and hence line l's slope must be equal to line y=1-x's slope... ->
sufficient.
stmt 2 - Line 'l' doesnt intersect y=x-1. It can intersect at any
angle...so slope cant be decided...

3. both x & y are positive

stmt 1: x > y => x > y^2 => x^3 > Y^6,
and since ^6 > y => x^3 > y -- -sufficient
stmt 2: x > y => x^3 > y ^3...and since y^3 x^3 > y - sufficient


Hi Alchemist,

Two queries:
1) In statement 2 question number 1, you have mentioned line L doesn't intersect y=x-1; However in actual question the statement 2 says

(2) Line l intersects the line with equation y = x - 1.
2) Question 3 - statement 1 says x > y ;
Here it can be 1/2 > 1/4
so x^3>y; (1/4)^3 >1/4; 1/64
If x > y => 2>1;
so x^3>y; (4)^3 >1; 64> 2 so x^3>y
Not sufficient
751
Hi Alchemist,

Two queries:
1) In statement 2 question number 1, you have mentioned line L doesn't intersect y=x-1; However in actual question the statement 2 says

(2) Line l intersects the line with equation y = x 1.
2) Question 3 - statement 1 says x > y ;
Here it can be 1/2 > 1/4
so x^3>y; (1/4)^3 >1/4; 1/64
If x > y => 2>1;
so x^3>y; (4)^3 >1; 64> 2 so x^3>y
Not sufficient


2. line 2 - it was a copy paste .... sorry.. but the explanation is correct..

3. Yep i missed the decimal part.. and thought them to be integers.....and yes..it is E.
752

hi,

can someone pls explain the soln. for this DS question?

thanks,
Raj

753
hi,

can someone pls explain the soln. for this DS question?

thanks,
Raj

My pick would be C.
754
hi,

can someone pls explain the soln. for this DS question?

thanks,
Raj


S= r * theta
convert theta into angle

18= angle in deg * pi *r/180

if we knw that r=s then it is an equilateral triangle with angle 60

so we can slve for r and hence get the circumference