GMAT Data Sufficiency Discussions

MBA GMAT
1861
Another two,

Is X greater than Y?
1. 6X=5Y
2. X^2


Statement 1:
==========
6x = 5y
x/y = 5/6 which means x/y
Statement 2:
==========
case1 : x = 0.1 and y =1 x y
so nt suff.

But combining both the statements we can arrive at a solution.So my take is option C
1862
Another two,

Is X greater than Y?
1. 6X=5Y
2. X^2



1. INSUFFICIENT

(2) if we take the sq.root on both sides , we get x
1863
1. INSUFFICIENT

(2) if we take the sq.root on both sides , we get x


dude had you considered the case when x and y are negative?
1864

OH MY GOD.............how can i slip this?.................................*bashes his head*

KILL ME ....................... KILL ME NOW !!!!!!!!!!!!!!!

1865
Statement 1:
==========
6x = 5y
x/y = 5/6 which means x/y
Statement 2:
==========
case1 : x = 0.1 and y =1 x y
so nt suff.

But combining both the statements we can arrive at a solution.So my take is option C


How do you arrive at a solution after combining both the statements? Can you please explain. Thanks
1866
pawank_iit Says
How do you arrive at a solution after combining both the statements? Can you please explain. Thanks


According to statement 2:x^2
so combining both the statements we can ans the q
1867
What was the percent increase in the average (arithmetic mean) contribution per member of a certain public radio station from 1985 to 1995 ?

(1) Total contributions by members increased from $505,210 in 1985 to $1,225,890 in 1995.
(2) The number of members exactly doubled from 1985 to 1995.

I believe it should be E. Because we do not know the number of people from either of the statements.
Assuming:

Total contributions by members in 1985 = X
Total contributions by members in 1995 = Y
The number of members in 1985 = a
The number of members in 1995 = b

We need ((Y/b) - (X/a))/(X/a)

We have X and Y from St 1
We know b = 2a from st 2.

But even after substituting b with 2a we need a to tell the %. So it should be E.
Please put in your opinions on this reasoning.
1868
According to statement 2:x^2 Now according to statement 1: x .

so combining both the statements we can ans the q


Statement 1 says that x = (5/6) y.
Now if y = -6 then x = -5... it means x > y
if y = 6 then x = 5 it means x Am I missing some thing?
1869

Let no. of members in 1985 = x
no. of members in 1995 = 2x

Contribution per member in 1985 = 505210/x
Contribution per member in 1995 = 1225890/2x
% change = (1225890/2x - 505210/x) / (505210/x)
= x will get cancel and we can find answer..
So C is the Answer..

What was the percent increase in the average (arithmetic mean) contribution per member of a certain public radio station from 1985 to 1995 ?
(1) Total contributions by members increased from $505,210 in 1985 to $1,225,890 in 1995.
(2) The number of members exactly doubled from 1985 to 1995.

I believe it should be E. Because we do not know the number of people from either of the statements.
Assuming:

Total contributions by members in 1985 = X
Total contributions by members in 1995 = Y
The number of members in 1985 = a
The number of members in 1995 = b

We need ((Y/b) - (X/a))/(X/a)

We have X and Y from St 1
We know b = 2a from st 2.

But even after substituting b with 2a we need a to tell the %. So it should be E.
Please put in your opinions on this reasoning.
1870

Got stumped in the following DS questions. : Need some detail explanation:

1>
foodcalories per kg|Grams of protein per KG
=============================================
S 2000 150
==============================================
T |1500 90

The table above gives the number of calories and grams of protein per
kilogram of foods S and T. If a total of 7 kilograms of S and T are combined
to make a certain food mixture, how many kilograms of food S are in the
mixture?

(1) The mixture has a total of 12,000
calories.
(2) The mixture has a total of 810
grams of protein.

2> S is a set of integers such that
i) if a is in S, then a is in S, and
ii) if each of a and b is in S, then ab is in S.
Is 4 in S?

(1) 1 is in S.
(2) 2 is in S.

Answer will be posted afterwards.

Regards,
Abhishek

1871
Total Mix is 7 Kg.. If S=x, T=7-x (Just one variable)
This can be easily solved by taking either case:-

Case 1) calorie = 12000 ==> S=5kg, T=2Kg
Case 2) protein = 810 ==> S=3kg, T=4kg
Answer = D
Got stumped in the following DS questions. : Need some detail explanation:

1>
foodcalories per kg|Grams of protein per KG
=============================================
S 2000 150
==============================================
T |1500 90

The table above gives the number of calories and grams of protein per
kilogram of foods S and T. If a total of 7 kilograms of S and T are combined
to make a certain food mixture, how many kilograms of food S are in the
mixture?

(1) The mixture has a total of 12,000
calories.
(2) The mixture has a total of 810
grams of protein.

Regards,
Abhishek
1872
Statement 1 says that x = (5/6) y.
Now if y = -6 then x = -5... it means x > y
if y = 6 then x = 5 it means x Am I missing some thing?


Hi Pawan,
Got missed somewhere in this q.You are correct.
1873
What was the percent increase in the average (arithmetic mean) contribution per member of a certain public radio station from 1985 to 1995 ?

(1) Total contributions by members increased from $505,210 in 1985 to $1,225,890 in 1995.
(2) The number of members exactly doubled from 1985 to 1995.

I believe it should be E. Because we do not know the number of people from either of the statements.
Assuming:

Total contributions by members in 1985 = X
Total contributions by members in 1995 = Y
The number of members in 1985 = a
The number of members in 1995 = b

We need ((Y/b) - (X/a))/(X/a)

We have X and Y from St 1
We know b = 2a from st 2.

But even after substituting b with 2a we need a to tell the %. So it should be E.
Please put in your opinions on this reasoning.


Each statements alone are nt suff to ans the q.But combining we can try if we can get the ans.

Let the no of ,members of '85 = 100 .So in '95 = 200.

Avg in '85 = x an Avg in '95 = y.So we can get the percentage value which will close to 20%

Let the no.of members in '85 = 50.So in '95 = 100.

Avg in '85 = x1 and in '95 = y1.When we roughly calculate the % increase we are closely getting 20%.

So my take on the above q is option C
1874
Got stumped in the following DS questions. : Need some detail explanation:

1>
foodcalories per kg|Grams of protein per KG
=============================================
S 2000 150
==============================================
T |1500 90

The table above gives the number of calories and grams of protein per
kilogram of foods S and T. If a total of 7 kilograms of S and T are combined
to make a certain food mixture, how many kilograms of food S are in the
mixture?

(1) The mixture has a total of 12,000
calories.
(2) The mixture has a total of 810
grams of protein.


For the above set

Q1. S+T = 7. so this can be converted to one variable.

statement 1 : 20s + 15(7-s) = 120..s can be found.
statement 2 : 15s + 9(7-s) = 81..S can be found.

so individual statements are suff to ans the q
1875


2> S is a set of integers such that
i) if a is in S, then a is in S, and
ii) if each of a and b is in S, then ab is in S.
Is 4 in S?

(1) 1 is in S.
(2) 2 is in S.



My take for the above set

S = { a,-a, b,-b ,ab}

statement 1:
==========
s = { 1,-1,a,b......} .Other elements can also be in the set .Nt suff

Statement 2:
==========
s = { 2,-2,a,b........} .Other elements can also be in set.Nt suff

Combining both the statements we get S = { 1,-1,2,-2,a,b.....}.So nt suff.

My take is option E
1876

Hi Deepak,

Thanks for the explanation. NO wonder I diddnt know how to approach it as it was a set based question.

Well the OA is B .

Even I think the OA is incorrect or the data insufficient to state the answer is B.

Regards,
Abhishek

My take for the above set

S = { a,-a, b,-b ,ab}

statement 1:
==========
s = { 1,-1,a,b......} .Other elements can also be in the set .Nt suff

Statement 2:
==========
s = { 2,-2,a,b........} .Other elements can also be in set.Nt suff

Combining both the statements we get S = { 1,-1,2,-2,a,b.....}.So nt suff.

My take is option E
1877

Hey puys,

sorry for the delay in posting the OAs. well, for the two inequalities questions i will post the OAs on Tuesday.

I see most of us (including me) have got the answers wrong and will just reconfirm the explanations from the key and post the same soon.

For the permutation & combination problem find the OA in bold below the question.

Apologises for the delay in posting the OAs. I encountered these questions during a practise test and can review them only from the computer on which i gave the test. I shall post the OAs for the rest of the questions by tuesday for sure.



In how many ways can 4 people A, B, C and D be seated such that B and C are always together.
1. A, B, C and D are to be seated in a row.
2. The distance between any person and his neighbour is 5 feet.

OA : D
The second case is considered as a circular arrangement.
1878
Hi Deepak,

Thanks for the explanation. NO wonder I diddnt know how to approach it as it was a set based question.

Well the OA is B .

Even I think the OA is incorrect or the data insufficient to state the answer is B.

Regards,
Abhishek


Anyone refuting this?OA is B(not agreed till now) whereas we agree on E.Can someone jump into this DS and solve it.
1879
deepakraam Says
Anyone refuting this?OA is B(not agreed till now) whereas we agree on E.Can someone jump into this DS and solve it.

Got stumped in the following DS questions. : Need some detail explanation:

2> S is a set of integers such that
i) if a is in S, then a is in S, and
ii) if each of a and b is in S, then ab is in S.
Is 4 in S?

(1) 1 is in S.
(2) 2 is in S.

Answer will be posted afterwards.

Regards,
Abhishek


Abhishek, is this given that b cant be equal to -a. Because if 2 is in the set then -2 is also in the set. Now since 2 and -2 are in the set we must have 2*-2 = -4 in the set. Hence 2 alone is sufficient. from 1 we cant get be sure about that.
1880
Got stumped in the following DS questions. : Need some detail explanation:


2> S is a set of integers such that
i) if a is in S, then a is in S, and
ii) if each of a and b is in S, then ab is in S.
Is 4 in S?

(1) 1 is in S.
(2) 2 is in S.


My take for the above set

S = { a,-a, b,-b ,ab}

statement 1:
==========
s = { 1,-1,a,b......} .Other elements can also be in the set .Nt suff

Statement 2:
==========
s = { 2,-2,a,b........} .Other elements can also be in set.Nt suff

Combining both the statements we get S = { 1,-1,2,-2,a,b.....}.So nt suff.

My take is option E

Hi Deepak,

Thanks for the explanation. NO wonder I diddnt know how to approach it as it was a set based question.

Well the OA is B .

Even I think the OA is incorrect or the data insufficient to state the answer is B.

Regards,
Abhishek


Posting after a long time ...
IMO ans B is correct ..

a and b are not necessarily distinct and also, b= -a is a possibility
So, S = {a,-a, b, -b, ab, -ab, -a^2, - b^2}

So, if a= 2, -a=-2 then we have two nos as 2 and -2 and their product is -4 .

So, -4 is in the set.