GMAT Data Sufficiency Discussions

[jha16june]

Originally Posted by ashishjha100

1.What is the rate, in cubic feet per minute, at which water is flowing into a certain rectangular tank?
(1) The height of the water in the tank is increasing at the rate of 2 feet per minute.
(2) The capacity of the tank is 216 cubic feet.
OA E
2. 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.
OA C

3.Pam and Ed are in a line to purchase tickets. How many people are in the line?
(1) There are 20 people behind Pam and 20 people in front of Ed.
(2) There are 5 people between Pam and Ed.
OA
pls help with reasoning.......

1. None of the statement is talking ne thing abt the time, which is indispensable for determining for rate. so answer is E.

2. x = ky, k is +ve
from 1, cannot say ne thing.
from 2, (x+2) = my, m is +ve. so cannot say ne thing.
from 1 and 2, 2 =2*1=1*2= y*(m-k), but y != 1, so y = 2. Hence E.

3.
from 1: 20 P*E 20 or E19P, so cannot say.
from 2: *E5P* or *P5E*, so cannot say ne thing. here * can be ne number.
from 1 and 2: 20P5E20 and 14E5P14 both satisfy the given conditions at a time. so cannot Say ne thing.
Hence the answer is E.

[ashishjha100]

Pls help........

[reddy.harikisho]

Originally Posted by ashishjha100

Pls help........

1. If ☉ denotes a mathematical operation, does
x☉y=y☉x for all x and y?
(1) For all x and y, x☉y = 2(x2 + y2).
(2) For all y, 0☉y = 2 y2

the question is, can u replace x with y in the given operation.
1 => if you replace x with y..it is gives the same result..so YES
2 => there is no information regarding x..so no.
So I think ans is A


2. What is the value of |x|?
(1) x = -|x|
(2) x2 = 4

1=> this does not give any information about value.
2=> x can be 2 or -2. But mod x is 2.. and we don’t need (1) to come to conclusion.
So I think ans is B


3.By what percent was the price of a certain candy bar increased?
(1) The price of the candy bar was increased by 5 cents.
(2) The price of the candy bar after the increase was 45 cents.

To answer the question, we need atleast two of these three: price before, price after, increased amount.
1=> only gives amount increased. So cannot answer alone
2=> give price after..cannot answer alone.
So we can answer using both 1 & 2. So ans is D
4. Are the numbers k/4, z/3 and r/2 in increasing order?
(1) 3 < z < 4
(2) r < z < k
1=> z is between 3 and 4. So 1<z/3<4/3. k and r can be +,- or zero. So we cant answer either yes or no to the question.
2=> z is between r and k..but either k or r can be +,- or zero. So we cant answer either yes or no to the question.
If u combine both..z is between 3 and 4 and between r and k..
r can be anything less or equal to 3. So r/2 =< 1.5.
z can be 1<z/3<1.33.
k can be greater than or equal to 4. So k/4 => 1
So we can have 1, 1.2, 1.5 OR 10, 1.2, 1
{the values or r and k can be other than those stated above. Because if z is 3.5 r can be 3.4 and k can be 3.6}
So answer is E.


5. If x ≠ 1, is y equal to x + 1?
(1) (y-2)/(x-1) = 1
(2) y2 = (x + 1)2
1=> if u replace y with x+1, the equation is satisfied
2=> same again.
So ans is D.

[ashishjha100]

Originally Posted by reddy.harikisho

1. If ☉ denotes a mathematical operation, does
x☉y=y☉x for all x and y?
(1) For all x and y, x☉y = 2(x2 + y2).
(2) For all y, 0☉y = 2 y2

the question is, can u replace x with y in the given operation.
1 => if you replace x with y..it is gives the same result..so YES
2 => there is no information regarding x..so no.
So I think ans is A


2. What is the value of |x|?
(1) x = -|x|
(2) x2 = 4

1=> this does not give any information about value.
2=> x can be 2 or -2. But mod x is 2.. and we don’t need (1) to come to conclusion.
So I think ans is B


3.By what percent was the price of a certain candy bar increased?
(1) The price of the candy bar was increased by 5 cents.
(2) The price of the candy bar after the increase was 45 cents.

To answer the question, we need atleast two of these three: price before, price after, increased amount.
1=> only gives amount increased. So cannot answer alone
2=> give price after..cannot answer alone.
So we can answer using both 1 & 2. So ans is D
4. Are the numbers k/4, z/3 and r/2 in increasing order?
(1) 3 < z < 4
(2) r < z < k
1=> z is between 3 and 4. So 1<z/3<4/3. k and r can be +,- or zero. So we cant answer either yes or no to the question.
2=> z is between r and k..but either k or r can be +,- or zero. So we cant answer either yes or no to the question.
If u combine both..z is between 3 and 4 and between r and k..
r can be anything less or equal to 3. So r/2 =< 1.5.
z can be 1<z/3<1.33.
k can be greater than or equal to 4. So k/4 => 1
So we can have 1, 1.2, 1.5 OR 10, 1.2, 1
{the values or r and k can be other than those stated above. Because if z is 3.5 r can be 3.4 and k can be 3.6}
So answer is E.


5. If x ≠ 1, is y equal to x + 1?
(1) (y-2)/(x-1) = 1
(2) y2 = (x + 1)2
1=> if u replace y with x+1, the equation is satisfied
2=> same again.
So ans is D.

last Q
5. If x ≠ 1, is y equal to x + 1?
(1) (y-2)/(x-1) = 1
(2) y^2 = (x + 1)^2
OA is A

[reddy.harikisho]

Originally Posted by ashishjha100

last Q
5. If x ≠ 1, is y equal to x + 1?
(1) (y-2)/(x-1) = 1
(2) y^2 = (x + 1)^2
OA is A

my bad.. y can be -(x+1) for the second statement.

wat is OA??

[ashishjha100]

Originally Posted by reddy.harikisho

my bad.. y can be -(x+1) for the second statement.

wat is OA??

Ans given is A

[*arch*]

Hi.. can someone plz help me with this question?

If a, b, and c are integers, is a-b+c > a+b-c ?

1) b is positive
2) c is negative

When you have a question that asks you whether one quantity is greater than the other with a common quantity present - for eg a+b > a+c (given b>c) do you need to know if a is +ve or -ve?

[ashishjha100]

Originally Posted by *arch*

Hi.. can someone plz help me with this question?

If a, b, and c are integers, is a-b+c > a+b-c ?

1) b is positive
2) c is negative

When you have a question that asks you whether one quantity is greater than the other with a common quantity present - for eg a+b > a+c (given b>c) do you need to know if a is +ve or -ve?

Here i think ans is C

eq bols down to c-b>b-c
1) b is positive
without c cant say anything....
2) c is negative
without b cant say anything....

Taking together c-b will always negative and b-c always positive.....so we will get result.....

When you have a question that asks you whether one quantity is greater than the other with a common quantity present - for eg a+b > a+c (given b>c) do you need to know if a is +ve or -ve?

u dont need to know as shown in eg above......

[abhishekag05]

ABCD is a rectangle, E is a point somewhere on side BC.
Is the area of triangle ABE > 25 ?

(1) AB = 6

(2) AE = 10

(A) Statement (1) alone is sufficient, but statement (2) alone is not sufficient.
(B) Statement (2) alone is sufficient, but statement (1) alone is not sufficient.
(C) BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
(D) Each statement ALONE is sufficient.
(E) Statements (1) and (2) TOGETHER are NOT sufficient.

[reddy.harikisho]

Originally Posted by abhishekag05

ABCD is a rectangle, E is a point somewhere on side BC.
Is the area of triangle ABE > 25 ?

(1) AB = 6

(2) AE = 10

for triangle ABE, AB= 6, BE = 10, SO BE = 8. {right angle triangle}
area = 1/2*base*height
1/2*6*8 = 24

So answer is C.