GMAT Data Sufficiency Discussions

MBA GMAT
501

If N>0, is N a whole number?

1) 3N is an odd number

For 3N to be an odd number, N cannot be even. Pick some numbers to try this out:-
Take N = 3; 3N = 9 (odd) and N is a whole number.
Take N = 7/3; 3N = 7 (odd) but N is not a whole number.

Hence Statement (1) is insufficient.

2) 2N is an even number

For 2N to be even; lets take
N = 2, 2N = 4;
N = 3, 2N = 6;
N = 3/2, 2N = 3 (not even)
N = 2/3, 2N = 4/3 (not even)

So the only case when 2N can be an even number, is when N is a whole number.

Hence statement (2) is Sufficient.

Answer is (B).



mittal.gaurav1 Says
The answer is B. Can u give me an explanation?
502

Pls help with reasoning.......OA are given........

503
ashishjha100 Says
Pls help with reasoning.......OA are given........

@ashishjha100, I will try to provide reason for 1-6 questions, Question 7 seems ambiguous and not sure of 8th.

Question - 1. d = 0.2h6. After rounding to nearest tenth, either d = 0.2 or 0.3
option-1: doption-2 : hoption is also sufficient.

Answer is D.

question - 2. k.(a+m) = (k.a) + (k.m) This will be true if and only if k = x (multiplication)
option-1 : k.l is not equal to l.k => k can't be multiplication. So, we got the answer, option-1 is sufficient.
option-2 : . represents subtraction and not multiplication. Thus, option-2 is sufficient.

Answer is D.

Question - 3. Is one angle of a quadrilateral is 60 degrees ?
option-1 : Two angles are 90 degrees. As there is no information as the
quadrilateral is regular or not, we can't be sure about other other 2 angles. Not sufficient.
option-2 : Angle B is twice of angle C, again as we are not sure as quadrilateral is regular, we can't apply any rule of geometry to calculate other 2 angles. Not sufficient.
option 1 & 2 together: two angles = 90 degrees but not sure as which angles are these. Angle B is twice of angle C but as dont know as which angle is 90 degree, can't calculate.

Answer is E. Interesting question, I did it wrong at first, but after finding answer, it strikes me that go to basics (no assumptions in GMAT)

Question - 4. As we know that Sum and Difference of two integers can be even if and only if both integers are either even or both are odd.
Option-1 and option-2 are not sufficient as there is no info about a.
Taking option-1 and 2 simultaneoulsy, (3a+5b) - (3a+4b) = even => b = even. Sufficient

Answer is D.

Question - 5.
Option-1 : Line passes through the point (0,2). That means, y intercept = 2. No information about x intercept. Not sufficient.
Option-2 : The y-intercept of the line is 2. That means, y intercept = 2. No information about x intercept. Not sufficient.
Option-1 and 2 together: Both give same info as y intercept = 2. No information about x intercept. Not sufficient.

Answer is E.

Question - 6. There is no information as x and y are positive or negative.
Option-1 : x/y = 7/9. Same ratio will come if both x and y are positive or both of them are negative. Not sufficient.
option-2 : xy>0. This means both x and y are non zero. xy will be greater than zero if both x and y are positive or both of them are negative. Not sufficient.
Option-1 and 2 together : still not able to figure out as x and y are positive or negative. Not sufficient.

Answer is E.

Question - 7. Fraction of an hour seems to create ambiguity. It can be 12 an hour, 1/4th of an
hour, 1/60 th of an hour. Not sure how to arrive at any answer. Try osting this question in PG again, we'll see what Junta thinks.
504
1.If x(x - 5)(x + 2) = 0, is x negative?
(1) x^2-7x 0

(2) x^2-2x -15 0

505
1.If x(x - 5)(x + 2) = 0, is x negative?
(1) x^2-7x 0

(2) x^2-2x -15 0



Ans . E

-Viv
506

Leo can buy a certain computer for p1 dollars in State A, where the sales tax is t1 percent,or he can buy the same computer for p2 dollars in State B, where the sales tax is t2 percent. Is the total cost of the computer greater in State A than in State B?
10
(1) t1 > t2
(2) p1t1 > p2t2
OA is E....pls help with reasoning......

507
Leo can buy a certain computer for p1 dollars in State A, where the sales tax is t1 percent,or he can buy the same computer for p2 dollars in State B, where the sales tax is t2 percent. Is the total cost of the computer greater in State A than in State B?
10
(1) t1 > t2
(2) p1t1 > p2t2
OA is E....pls help with reasoning......


to solve this one we need relations between t1 and t2 & p1 and p2. total cost would be p1+t1/100, p2+t2/100.
1-> gives the relation between taxes, no info about p. so not sufficient
2-> with this statement, either p1, t1 > p2, t2 OR p1, t2 > p2, t1 OR t1, t2 > p1,p2 . so there are lot of possibilities. not sufficient.

if we take two statements together, there are still two possibilities.

So E.
508

During a 10-week summer vacation, was the average (arithmetic mean) number of
books that Carolyn read per week greater than the average number of books that Jacob
read per week?
(1) Twice the average number of books that Carolyn read per week was greater
than 5 less than twice the average number of books that Jacob read per week.
(2) During the last 5 weeks of the vacation, Carolyn read a total of 3 books more
than Jacob.
OA A

2.Does the decimal equivalent of P/Q, where P and Q are positive integers, contain only a finite number of nonzero digits?
(1) P>Q
(2) Q=8
OA E
3.A certain carton holds fewer than 50 books. What is the number of books in the
carton?
(1) The books in the carton can be divided into 3 stacks of X books each, with 2
books left over.
(2) The books in the carton can be divided into Y stacks of 7 books each, with 2
books left over.
OA E

509

Solved them before..some OA's given are wrong.

During a 10-week summer vacation, was the average (arithmetic mean) number of
books that Carolyn read per week greater than the average number of books that Jacob
read per week?
(1) Twice the average number of books that Carolyn read per week was greater
than 5 less than twice the average number of books that Jacob read per week.
(2) During the last 5 weeks of the vacation, Carolyn read a total of 3 books more
than Jacob.
OA A

asked ..IS C>J

1) => 2C > 2J-5 => C> J-2.5 . so C can be J-2,J-1,J,J+1 and so on. essentially C can be J..hence insufficient
2) obly insuff..

OA..E

 2.Does the decimal equivalent of P/Q, where P and Q are positive integers, contain only a finite number of nonzero digits?
(1) P>Q
(2) Q=8
OA E

1)=> insuff.. it can be 5/4 or 8/7..
2) => p/q = 0.125P . if P is a +ve integer this always contains a finite number of non zero digits. i.e it doesn't have recurring decimal for sure. so suff

OA B

 3.A certain carton holds fewer than 50 books. What is the number of books in the
carton?
(1) The books in the carton can be divided into 3 stacks of X books each, with 2
books left over.
(2) The books in the carton can be divided into Y stacks of 7 books each, with 2
books left over.
OA E

1) => n= 3x+2 ..we can put many values for x such that we get n
2)=> n = 7y+2..again many y's to given n
both combined => 3x = 7y . so n can be 21, 42. insuff

hence OA E




Neo
510
1.If x(x - 5)(x + 2) = 0, is x negative?


(1) x^2-7x 0

(2) x^2-2x -15 0


@ ashishjha, what's the correct answer for this, I think it should be option C.
My reasoning -
As x(x - 5)(x + 2) = 0, possible values for x are : 0 or 5 or -2.

Considering option-1 : x^2-7x 0 => x(x-7) 0 => x 0. This option only says that x 0. Not-sufficient.

Considering option-2 : x^2-2x -15 0 => (x+3)(x-5) 0 => x -3 and x 5. This option only cancels out that x 5. Not sufficient.
Considering option 1 & 2 simultaneously : x 0 and x 5. So x has to be -2 and thats a negative number. So, taking both option 1 & 2, we found the answer that x is negative (Sufficient). So, the answer should be C.
Please provide the correct option, I could be wrong as my status is still 'trainee - newbie' 😉
511

Plz help with this..
What is the Value of Ix+7I (absolute values)?
1) Ix+3I = 14
2) (x+2)^2 = 169
OA is D. Mine is C.

512

Yes it must be C

From 1 we have two values of x -> -17 and 11 -> No definite answer (Insufficient)

From 2 we have again 2 values of x -> 11 and -15 - Insufficient

From 1 and 2 together -> x= 11 so x+7 can be computed..


Thanks
KKC

513
Plz help with this..
What is the Value of Ix+7I (absolute values)?
1) Ix+3I = 14
2) (x+2)^2 = 169
OA is D. Mine is C.


It should be C only as only after taking both the options into considerations we'll get unique value of x and hence x+7.
514
@ashishjha100, I will try to provide reason for 1-6 questions, Question 7 seems ambiguous and not sure of 8th.

Question - 1. d = 0.2h6. After rounding to nearest tenth, either d = 0.2 or 0.3
option-1: doption-2 : hoption is also sufficient.

Answer is D.

question - 2. k.(a+m) = (k.a) + (k.m) This will be true if and only if k = x (multiplication)
option-1 : k.l is not equal to l.k => k can't be multiplication. So, we got the answer, option-1 is sufficient.
option-2 : . represents subtraction and not multiplication. Thus, option-2 is sufficient.

Answer is D.

Question - 3. Is one angle of a quadrilateral is 60 degrees ?
option-1 : Two angles are 90 degrees. As there is no information as the
quadrilateral is regular or not, we can't be sure about other other 2 angles. Not sufficient.
option-2 : Angle B is twice of angle C, again as we are not sure as quadrilateral is regular, we can't apply any rule of geometry to calculate other 2 angles. Not sufficient.
option 1 & 2 together: two angles = 90 degrees but not sure as which angles are these. Angle B is twice of angle C but as dont know as which angle is 90 degree, can't calculate.

Answer is E. Interesting question, I did it wrong at first, but after finding answer, it strikes me that go to basics (no assumptions in GMAT)

Question - 4. As we know that Sum and Difference of two integers can be even if and only if both integers are either even or both are odd.
Option-1 and option-2 are not sufficient as there is no info about a.
Taking option-1 and 2 simultaneoulsy, (3a+5b) - (3a+4b) = even => b = even. Sufficient

Answer is D.

Question - 5.
Option-1 : Line passes through the point (0,2). That means, y intercept = 2. No information about x intercept. Not sufficient.
Option-2 : The y-intercept of the line is 2. That means, y intercept = 2. No information about x intercept. Not sufficient.
Option-1 and 2 together: Both give same info as y intercept = 2. No information about x intercept. Not sufficient.

Answer is E.

Question - 6. There is no information as x and y are positive or negative.
Option-1 : x/y = 7/9. Same ratio will come if both x and y are positive or both of them are negative. Not sufficient.
option-2 : xy>0. This means both x and y are non zero. xy will be greater than zero if both x and y are positive or both of them are negative. Not sufficient.
Option-1 and 2 together : still not able to figure out as x and y are positive or negative. Not sufficient.

Answer is E.

Question - 7. Fraction of an hour seems to create ambiguity. It can be 12 an hour, 1/4th of an
hour, 1/60 th of an hour. Not sure how to arrive at any answer. Try osting this question in PG again, we'll see what Junta thinks.


for question No 7:
7. For each landscaping job that takes more than 4 hours, a certain contractor charges a total of r dollars for the first 4 hours plus 0.2r dollars for each additional hour or fraction of an hour, where r>100. Did a particular landscaping job take more than 10 hours?

(1) The contractor charges a total of $288 for the job
(2) The contractor charges a total of 2.4r dollars for the job.

Lets assume that total extra hours =x (excluding normal 4 hours work)
now lets take first statement
1) as total charges =$288
=> r + .2r*x = 288
now r>100 lets take r as 110 ( to make calculation simpler)
110 +22x=288 => 22x = 177 => x =8.04(approx)

so total hours = 4 + x = 12.04

now lets take r =200
=> 200 + 40x = 288 => 40x =88 => x = 2.2

so total hours = 4 + x = 6.2

so statement one not sufficent

Now lets take statement 2
2)
total charge = 2.4r
=> r+ .2r*x=2.4r
.2r*x = 1.4r
.2x=1.4 => x=7

total hours = 4 + x = 11 hence greater than 10

so second is sufficient
hence B

Correct me if i am not
515

If z^n = 1, what is the value of z?
1. n is a non-zero integer
2. z > 0

I guess the answer is A but OA is C.

516

Another one -
What is value of a^4 - b^4 ?
1. a^2 - b^2 = 16
2. a + b = 8

I think answer should be A because if a^2 - b^2 = 16, a = 5 and b = 3 is the only solution possible.
But the OA is C.

517
Another one -
What is value of a^4 - b^4 ?
1. a^2 - b^2 = 16
2. a + b = 8

I think answer should be A because if a^2 - b^2 = 16, a = 5 and b = 3 is the only solution possible.
But the OA is C.

But we are not told in the question that a & b are integers....ur assumption is valid in case of integers only......so A is not sufficient......Ans is C itself.....hope this helps.....
518
If z^n = 1, what is the value of z?
1. n is a non-zero integer
2. z > 0

I guess the answer is A but OA is C.


If u consider (1), then z can be -1 or 1 (with n=2). Hence, we can't deduce the value of z with only (1). You will need (2) to narrow the choice between -1 and 1 and since (2) states z>0, that makes it clear that z=1. Hence the answer is C.
519
vikram_1982 Says
If u consider (1), then z can be -1 or 1 (with n=2). Hence, we can't deduce the value of z with only (1). You will need (2) to narrow the choice between -1 and 1 and since (2) states z>0, that makes it clear that z=1. Hence the answer is C.


yes..ans is indeed C..
z^n = 1 when either n is zero OR Z=1 OR Z=-1 with even power..

combining 2 statements gives us z=1
520
Another one -
What is value of a^4 - b^4 ?
1. a^2 - b^2 = 16
2. a + b = 8

I think answer should be A because if a^2 - b^2 = 16, a = 5 and b = 3 is the only solution possible.
But the OA is C.


Never ever assume anything. You assumed that a and b are integers, dont fall in these traps which Gmat throws ocassionally.

a^4 - b^4 = (a^2 - b^2)(a^2 + b^2). For calculating the value of expression, we need to know the values of both (a^2 - b^2) and (a^2 + b^2).

Considering option A - It gives only the value of (a^2 - b^2) but we can't calculate the value of (a^2 + b^2). Not sufficient.

Considering option B - a + b = 8. Can't calculate values for (a-b) and (a^2 + b^2). Not sufficient.

Considerting both A and B simultaneously - (a^2 - b^2) = 16 and a+b=8.
using both these expressions, you can calculate the value of ab and from that the value of (a^2 + b^2). Sufficient.

Answer is C