GMAT Data Sufficiency Discussions

MBA GMAT
1061
Well.. it took me very long to understand where you went wrong.. when I solved it on my own I got answer as option A only, but then your explanation almost got me convinced, till I noticed the highlighted section..

Your assumption of x = 9 and z = 9.1 is NOT supported in the questions, as per option A, Z is closer to 10 than it is to X.. now try and substitute suitable values and you would find that option A is sufficient..

Hope this helps!!


9.1 is closer to 10 than 9 is to 10. Shud I take only integer values?
1062

Hi Ramviswa,
This is a silly mistake you did. You understood the question wrong. Z is closer to 10 than it is to X....
so for your choice ....9.1 should be closer to 10 than the closeness of 9.1 with 9.
9.1 is not closer to 10 than 9.1 is to 9......

1063
This is a question (q no.99) from GMAT Quants review book.

1. If x is 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 answer is E whereas OA is A.

My explanation
1) If x = 1 and z = 9, z is greater than mean
If x = 9 and z = 9.1 z is less than mean
Insufficient
2) If x = 1 z = 5 then zmean
Insufficient

Comb. 1 and 2
We can apply the same conditions as applied for 2) - Insufficient

Please share your thoughts.


Hey ram ...

Varun and Amar have already helped u correct ur silly mistake ...

Basically, had z been equidistant from x and 10 ...it wud have been the average of x and 10 ...

When z is closer to 10 than x, it is always greater than mean ...Hence sufficient ...Ans A...
1064
ramviswa Says
9.1 is closer to 10 than 9 is to 10. Shud I take only integer values?


well.. not really sure, but I think I read somewhr on PGuy only that until unless specified all the number in GMAT Quant section are real numbers. SO since here it was not defined as X or Z being integers, they could be a any real number..

You were right in the number sense as far as your assumption was concerned, the only thing that got you was the value.. No big deal..everyone does that once in a while!! :
1065

Pls help with this question ..

Is z an integer?

1. z^3 is an integer
2. 3z is an integer

1066
Pls help with this question ..

Is z an integer?

1. z^3 is an integer
2. 3z is an integer


Option 1:
Z^3 is an integer... NOT sufficient;
(1.81)^3 = 6
&
(2)^3 = 8

Option 2:
3z is an integer... NOT Sufficient
3(0.667) = 2
&
3(2) = 4

So far answer option A, B and D have been ruled out.
The answer would be either C or E. Let's see... :sneaky:

I would have chosen option C. Bcoz I dont think there can be a non-integer that when multiplied by 3 is integer and also when raised to power of 3 remains an integer.

My answer would have been option C :lookround:
1067
Pls help with this question ..

Is z an integer?

1. z^3 is an integer
2. 3z is an integer


1) Z has to be an integer for Z^3 to be an integer. sufficient
2) Z can be 2 or 1/3. Insufficient

My answer is A.
1068

1. z^3 is an integer
2. 3z is an integer
for 1st statement - if z^3 is an integer, z is always an integer.
for 2nd statment - if 3z is an intger, z can be integer or fraction.
e.g. z can be 1,2,3.......or 1/3,2/3,4/3....
So 1 alone is sufficient to answer the question.
The answer should be A.

1069
Option 1:
Z^3 is an integer... NOT sufficient;
(1.81)^3 = 6
&
(2)^3 = 8

Option 2:
3z is an integer... NOT Sufficient
3(0.667) = 2
&
3(2) = 4

So far answer option A, B and D have been ruled out.
The answer would be either C or E. Let's see... :sneaky:

I would have chosen option C. Bcoz I dont think there can be a non-integer that when multiplied by 3 is integer and also when raised to power of 3 remains an integer.

My answer would have been option C :lookround:


I was wrong. After looking at Varun's answer, I think the answer should be C.

My explanation goes like:

if z^3 is an integer, it is not necessary that z is always an integer.
e.g. if z is cubrt(3)
so 1 alone cannot answer the question.
for 2nd statment - if 3z is an intger, z can be integer or fraction.
e.g. z can be 1,2,3.......or 1/3,2/3,4/3....
So 2 alone cannot answer the question.
if both statements are true.....
z^3 = I1
3z = I2
From these two equations, (I2/3)^3 = I1
i.e. (I2)^3 = 27I1
For I1 to be an integer I2 should be multiple of 3.
So, values of I2 = 3,6,9,12,15
corresponding values of I1 = 1,8, 27,64......
So in all these cases z is an integer.
So both the statements are needed to answer the question.
The answer should be C.
1070
Pls help with this question ..

Is z an integer?

1. z^3 is an integer
2. 3z is an integer

Option 1:
Z^3 is an integer... NOT sufficient;
(1.81)^3 = 6
&
(2)^3 = 8

Option 2:
3z is an integer... NOT Sufficient
3(0.667) = 2
&
3(2) = 4

So far answer option A, B and D have been ruled out.
The answer would be either C or E. Let's see... :sneaky:

I would have chosen option C. Bcoz I dont think there can be a non-integer that when multiplied by 3 is integer and also when raised to power of 3 remains an integer.

My answer would have been option C :lookround:

1) Z has to be an integer for Z^3 to be an integer. sufficient
2) Z can be 2 or 1/3. Insufficient

My answer is A.

1. z^3 is an integer
2. 3z is an integer
for 1st statement - if z^3 is an integer, z is always an integer.
for 2nd statment - if 3z is an intger, z can be integer or fraction.
e.g. z can be 1,2,3.......or 1/3,2/3,4/3....
So 1 alone is sufficient to answer the question.
The answer should be A.


gud one guys !!!!
1071

i have a question

Q. John travels from A to B in 1/2 hrs. Is the distance between A & b greater than 6 miles ??

( 1 mile = 5028 feet ) ( Not sure about the conversion factor, please check once )

1) John's speed is greater than 16ft/sec
2) John's speed is less than 18 ft/sec

1072
i have a question

Q. John travels from A to B in 1/2 hrs. Is the distance between A & b greater than 6 miles ??

( 1 mile = 5028 feet ) ( Not sure about the conversion factor, please check once )

1) John's speed is greater than 16ft/sec
2) John's speed is less than 18 ft/sec


I guess the ans is E ...

before evaluating statements ...we need to calculate the cutoff speed for a distance eq to 6 miles in hf hr ...

yes conversion factor holds true ...
(1 mile = 1.6 kms = 1600m = 1600 * 10/3 feet = 16000/3 feet )
Hence, 6 miles = 32000 feet ...
1/2 hr = 1800 sec

hence, cut off speed = 32000 /1800 = 17.xx ft/ sec...

So, from statements if range is clearly above or below 17.xx , it is sufficient..

Even after combining statement ...not sufficient ...
Hence, Ans is E ....
1073
i have a question

Q. John travels from A to B in 1/2 hrs. Is the distance between A & b greater than 6 miles ??

( 1 mile = 5028 feet ) ( Not sure about the conversion factor, please check once )

1) John's speed is greater than 16ft/sec
2) John's speed is less than 18 ft/sec


My answer is D. Because with both options we can find out the distance that John as travel. My assumption here is that john travels at a constant speed in 1/2 hour. If my assumption is wrong, then the answer is E.
1074
ramviswa Says
My answer is D. Because with both options we can find out the distance that John as travel. My assumption here is that john travels at a constant speed in 1/2 hour. If my assumption is wrong, then the answer is E.


hi ram ...yes u can assume that John travels with a constant speed for entire journey..
but the problem is that we dont know what that constant speed is ...

eg
St 1 : we are free to choose any constant speed above 16 ft / sec...

if S = 17 ft/sec (any speed below cut off speed of 17.xx and above 16 ), distance travelled is less than 6 miles

If S = 18 ft/sec (any speed above cut off speed of 17.xx ), distance travelled is more than 6 miles..

Similarly for st 2 ...

even combined st does not give us anything ..

Hope this helps !!
1075
hi ram ...yes u can assume that John travels with a constant speed for entire journey..
but the problem is that we dont know what that constant speed is ...

eg
St 1 : we are free to choose any constant speed above 16 ft / sec...

if S = 17 ft/sec (any speed below cut off speed of 17.xx and above 16 ), distance travelled is less than 6 miles

If S = 18 ft/sec (any speed above cut off speed of 17.xx ), distance travelled is more than 6 miles..

Similarly for st 2 ...

even combined st does not give us anything ..

Hope this helps !!



if we assume speed constant or not it doesnt make any sense

because

st1 greater then 16

if 16.1 then distance =28980

if 17 then distance=30600

here 6 mile=30168

means st1 not sufficient

from 2

less than 18

so if speed greater than 16.7X than distance more than 30168

but if less than 16.7x than distance less than 30168

so not sufficient

if we combine both then speed any from 16>x>18

so distance 28800>d>32400

so ans is E

data didnt say speed is the integer value
1076
hi ram ...yes u can assume that John travels with a constant speed for entire journey..
but the problem is that we dont know what that constant speed is ...

eg
St 1 : we are free to choose any constant speed above 16 ft / sec...

if S = 17 ft/sec (any speed below cut off speed of 17.xx and above 16 ), distance travelled is less than 6 miles

If S = 18 ft/sec (any speed above cut off speed of 17.xx ), distance travelled is more than 6 miles..

Similarly for st 2 ...

even combined st does not give us anything ..

Hope this helps !!


Yes, I didnt read the q properly. Answer is E.
1077

Q1: Are x and y both positive?
1) 2x-2y=1
2) x/y >1

Q2: Is m+z>0 ?
1) m-3z>0
2) 4z-m>0

Q3: If integers a and n are greater than 1 and the product of the first 8 positive integers is a multiple of an, what is the value of a?
1) an = 64 2) n = 6

Q4: What is the remainder when posiytive integer x is divided by 6?
1) When x is divided by 2, the remainder is 1; and when x is divided by 3, the remainder is 0.
2) When x is divided by 12, the remainder is 3.

Q5: At a certain company, average (aritmetic mean) number of years of experience is 9.8 years for male employees and 9.1 years for female employees. What is the ratio of the number of company's male employees to the number of company's female employees?
1) There are 52 male employees at the company.
2) Average number of years of experience for the company's male and female employees combined is 9.3 years.


1078
Q1: Are x and y both positive?
1) 2x-2y=1
2) x/y >1

Q2: Is m+z>0 ?
1) m-3z>0
2) 4z-m>0

Q3: If integers a and n are greater than 1 and the product of the first 8 positive integers is a multiple of an, what is the value of a?
1) an = 64 2) n = 6

Q4: What is the remainder when posiytive integer x is divided by 6?
1) When x is divided by 2, the remainder is 1; and when x is divided by 3, the remainder is 0.
2) When x is divided by 12, the remainder is 3.

Q5: At a certain company, average (aritmetic mean) number of years of experience is 9.8 years for male employees and 9.1 years for female employees. What is the ratio of the number of company's male employees to the number of company's female employees?
1) There are 52 male employees at the company.
2) Average number of years of experience for the company's male and female employees combined is 9.3 years.




My answers are

1. C
2. E
3. E
4. D
5. B

I will post my explanation if my answers are right.
1079
Q1: Are x and y both positive?
1) 2x-2y=1
2) x/y >1

Q2: Is m+z>0 ?
1) m-3z>0
2) 4z-m>0

Q3: If integers a and n are greater than 1 and the product of the first 8 positive integers is a multiple of an, what is the value of a?
1) an = 64 2) n = 6

Q4: What is the remainder when posiytive integer x is divided by 6?
1) When x is divided by 2, the remainder is 1; and when x is divided by 3, the remainder is 0.
2) When x is divided by 12, the remainder is 3.

Q5: At a certain company, average (aritmetic mean) number of years of experience is 9.8 years for male employees and 9.1 years for female employees. What is the ratio of the number of company's male employees to the number of company's female employees?
1) There are 52 male employees at the company.
2) Average number of years of experience for the company's male and female employees combined is 9.3 years.




1. C
2. C
3. guess some error in sum ...else C
4. D
5. B

will post my reasoning in a while ...
1080
Q1: Are x and y both positive?
1) 2x-2y=1
2) x/y >1

Q2: Is m+z>0 ?
1) m-3z>0
2) 4z-m>0

Q3: If integers a and n are greater than 1 and the product of the first 8 positive integers is a multiple of an, what is the value of a?
1) an = 64 2) n = 6

Q4: What is the remainder when posiytive integer x is divided by 6?
1) When x is divided by 2, the remainder is 1; and when x is divided by 3, the remainder is 0.
2) When x is divided by 12, the remainder is 3.

Q5: At a certain company, average (aritmetic mean) number of years of experience is 9.8 years for male employees and 9.1 years for female employees. What is the ratio of the number of company's male employees to the number of company's female employees?
1) There are 52 male employees at the company.
2) Average number of years of experience for the company's male and female employees combined is 9.3 years.




my reasoning ...

Prob 1 :

St 1 : x is greater than y by 1/2...nothing else ...not sufficient ..
St 2 : absolute value of x is greater than y ...both x and y are either positive or both negative... not sufficient ...

Combined 1 n 2 : we need x>y and absolute value of x > absolute value of Y ...hence x and y are necessarily positive....sufficient ...

Ans C
Prob 2 :

St 1: m>3z ...nothing can be said about m and z...both can be +ve, -ve or m +ve n z -ve ....not suff...

St 2 : m
Combined 1 & 2 : 3z
Hence, Ans C ...
Prob 3:

We have, 8! = k*an (where k is some integer value) ..

St1 : an = 64...we dont arrive at specific value of a ...not suff..
St2 : n = 6 ....we dont have a specific value of k and hene no specific value of a ...not suff..

Combined 1 and 2:
If an = 64 and n =6 ...we dont get a integer value for a ...violates the sum ...is there any typo error ?? ...else we have specific value for a...suff...

Hence, Ans C