GMAT Data Sufficiency Discussions

MBA GMAT
542
Guyz pl help me wid this.....got stuck with relatively easy probs:

1) In a survey of 150 persons, how many were smokers and drinkers?
(I) 80% of the person surveyed were drinkers
(II) 40% of the smokers were drinkers also

pl explain ur method while selecting ur answer....


I think the answer should be B as option B indentifies smokers who were smokers i.e these persons both smoke and drink. So, 40% persons were smokers and drinkers.

Please let us know the OA.

Thanks
543
I think the answer should be B as option B indentifies smokers who were smokers i.e these persons both smoke and drink. So, 40% persons were smokers and drinkers.

Please let us know the OA.

Thanks

i chose C

From Stem 1:
120 persons drink.......not sufficient
From Stem 2:
40% of smokers drink......not suff as we dot knw the % who smoke

Combining both:
Let n(Smoke) = x
Then % who smoke n drink = 0.4x (intersecion region of 2 circles in venn diagram)

No. of ppl who only smoke = o.6x
No. of ppl who only drink = 120-0.4x

Hence, 0.6x+0.4x+120-0.4x = 150.....which can be solved for x
Therefore answer C

But the OA is E as their logic is that since it's not mentioned abt the no. of ppl who don't smoke nor drink, it can't be found out.

But my reasoning is that unless otherwise stated, we hv to assume that there is no onw who does nothing.

Does my reasoning have a flaw?

thanks
544

Please bear with me for posting attachments....Please provide explanations with your answers

545

1.
1. x<.88 as="" not="" sufficient="" unknown="" y="">2. y<.17 as="" not="" sufficient="" unknown="" x="">Combining if x=.86 & y=.16 x+y>1
x=-.86 & y=-.16 x+y
So ans E

546
Find the fourth consecutive even number:
(I) The sum of the last two numbers is 30
(II) The sum of the first two numbers is 22

Let no:s be x,x+2,x+4,x+6

1. x+4+x+6=30

so x=10 and 4th term is 16

2. x+x+2=22

so x=10 and 4th term is 16

So ans D

ashish i understand that there can only be 2 consecutive integers whose sum is 30 n they r 14 and 16. But based on this u can't say which will be the 4th consec integer since we do not knw the no. of terms in the series, nor the frst term.
consider the case when the series is 8,10,12,14,16.In this case last 2 integers sum up to 30 and the 4th consec even int is 14. Consider another series where the series is 10,12,14,16. Again the sum of last 2 int add up to 30 and the 4th consec even int is 16. The point is we do not knw the first term hence statement 1 is not suff.

But frm B, x+(x+2) = 22......x = 10
As we knw the 1st term, the 4th no in the series is 16......Stem b is suff

Hence i chose B.

Is my logic correct?
547
naveen_petrucci Says
Please bear with me for posting attachments....Please provide explanations with your answers

Hi Naveen,

I am giving below answers and explanations for all of them except 4th.

1. Is x + y
Option - A : x Option - B : y Option A and B : x Answer is E.
2. Was country X among 6 highest contributing countries ?

Option - A : There is no way we can find out whether country X is amongst top 6. Not sufficient.
Option - B : Country X paid 4.8 % of total expenditure. There is no indication as how much was the individual contribution of top 6 contributing countries. So, we can not come to any conclusion. Not sufficient.
Option A and B : 56% is paid collectively by 4 top paying countries (i.e next 2 countries total contribution will be 11.8%) and X paid 4.8 % but still we can not be sure as X is amongst those 2 companies or not because their individual contribution could be 6 and 5.8 % or 7 and 4.8 %. Not sufficient.
Answer is E.
3. Is x even ?

Option - A : x(y+5) = even. There could be three possibilities - (x even, y odd) OR (x even, y even) OR (x odd, y odd). Not suffcient.
Option - B : 6y^2 + 41y + 25 = even. => This shows that y can only be odd. but there is no info about x, so Not sufficient.
Option A and B : From B, we know that y is even. But as per above written possibilities, x can still be even or odd. so. Not sufficient.
Answer is E.
5. x and y are integers. X > 0. Is y > 0 ?

Option - A : 7x - 2y > 0 => 7x > 2y. y can be +ve or -ve. Not sufficient.
Option - B : -y Option A and B : Again y can can be both +ve or -ve depending on values of x and y and we dont know the velues. So, Not sufficient
Answer is E.

Hope it helps...
548

Thanks dopa for the explanations, heres one more



The following problems contain a question and two statements giving certain data. You have to decide whether the data given in the statements are sufficient for answering the questions. The alternatives available are:
If * denotes a mathematical operation, does X* Y = Y * X for all X and Y?
(A) For all X and Y, X * Y = 2 (X^2 + Y^2)
(B) For all Y, 0 * Y = 2Y^2




1. statement (A) alone is sufficient but statement (B) alone is not
2. statement (B) alone is sufficient but statement (A) alone is not
3. both (A) and (B) together are sufficient but none of them alone is sufficient
4. both statements independently are sufficient
5. both (A) and (B) together are not sufficient

549

If * denotes a mathematical operation, does X* Y = Y * X for all X and Y?
(A) For all X and Y, X * Y = 2 (X^2 + Y^2)
(B) For all Y, 0 * Y = 2Y^2

Answer should be A.
does X* Y = Y * X for all X and Y?
Option - A : X * Y = 2 (X^2 + Y^2) is true for all X and Y. So, Y * X = 2(Y^2 + X^2).
And 2 (X^2 + Y^2) = 2(Y^2 + X^2) for all values of X and Y. So, X* Y = Y * X
Sufficient.

Option - B : Y, 0 * Y = 2Y^2. There is no information about X here so we can't be sure. Not sufficient.

Is A the OA ?
550

Yes Dopa the OA is A.


a few more :)

1) If digit h is the hundredths' digit in the decimal d = 0.2h6, what is the value of d, rounded to the nearest tenth?
(A) d (B) h

1. statement (A) alone is sufficient but statement (B) alone is not
2. statement (B) alone is sufficient but statement (A) alone is not
3. both (A) and (B) together are sufficient but none of them alone is sufficient
4. both statements are sufficient independently
5. both (A) and (B) together are not sufficient



2) If X is an integer, is (X + p) (X + q) an even integer?
(A) q is an even integer.
(B) p is an even integer.
1. statement (A) alone is sufficient but statement (B) alone is not
2. statement (B) alone is sufficient but statement (A) alone is not
3. both (A) and (B) together are sufficient but none of them alone is sufficient
4. both statements are sufficient independently
5. both (A) and (B) together are not sufficient

3) A total of 774 doctorates in mathematics were granted to United States citizens by American universities in the 1972-1973 school year, and W of these doctorates were granted to women. The total of such doctorates in the 1986-1987 school year was 362, and w of these were granted to women. If the number of doctorates in mathematics granted to female citizens of the United States by American universities decreased from the 1972-1973 school year to the 1986-1987 school year, was the decrease less than 10 percent?
(A) 1/10 (B) W = w + 5

1. statement (A) alone is sufficient but statement (B) alone is not
2. statement (B) alone is sufficient but statement (A) alone is not
3. both (A) and (B) together are sufficient but none of them alone is sufficient
4. both statements are sufficient independently
5. both (A) and (B) together are not sufficient

4) If a bottle is to be selected at random from a certain collection of bottles, what is the probability that the bottle will be defective?
(A) The ratio of the number of bottles in the collection that are defective to the number that are not defective is 3:500.
(B) The collection contains 3,521 bottles.

1. statement (A) alone is sufficient but statement (B) alone is not
2. statement (B) alone is sufficient but statement (A) alone is not
3. both (A) and (B) together are sufficient but none of them alone is sufficient
4. both statements are sufficient independently
5. both (A) and (B) together are not sufficient

551
Thanks dopa for the explanations, heres one more



The following problems contain a question and two statements giving certain data. You have to decide whether the data given in the statements are sufficient for answering the questions. The alternatives available are:
If * denotes a mathematical operation, does X* Y = Y * X for all X and Y?
(A) For all X and Y, X * Y = 2 (X^2 + Y^2)
(B) For all Y, 0 * Y = 2Y^2




1. statement (A) alone is sufficient but statement (B) alone is not
2. statement (B) alone is sufficient but statement (A) alone is not
3. both (A) and (B) together are sufficient but none of them alone is sufficient
4. both statements independently are sufficient
5. both (A) and (B) together are not sufficient

Its A

From Stem 1: X*Y = 2(X^2+Y^2)
Interchanging, we get Y*X = 2(Y^2+X^2)
Hence Y*X=X*Y

From Stem 2: 0*Y= 2Y^2.....since no info is available abt X, its not suff

OA is A
552
Yes Dopa the OA is A.
a few more :)



Dude, please dont paste all the 5 options while posting DS questions, just post the questions alone...because these 5 options are same for each and every DS questions in GMAT and most importantly they chew up the crucial space of PG's database.

Other Puys - Please dont re-quote the long posts you are replying to, edit it and quote only the relevant part of the same.

here are my answers -
1.D
2.E
3.C
4.A

Are these the OAs ?
553
Yes Dopa the OA is A.


a few more :)

1) If digit h is the hundredths' digit in the decimal d = 0.2h6, what is the value of d, rounded to the nearest tenth?
(A) d (B) h

1. statement (A) alone is sufficient but statement (B) alone is not
2. statement (B) alone is sufficient but statement (A) alone is not
3. both (A) and (B) together are sufficient but none of them alone is sufficient
4. both statements are sufficient independently
5. both (A) and (B) together are not sufficient



2) If X is an integer, is (X + p) (X + q) an even integer?
(A) q is an even integer.
(B) p is an even integer.
1. statement (A) alone is sufficient but statement (B) alone is not
2. statement (B) alone is sufficient but statement (A) alone is not
3. both (A) and (B) together are sufficient but none of them alone is sufficient
4. both statements are sufficient independently
5. both (A) and (B) together are not sufficient

3) A total of 774 doctorates in mathematics were granted to United States citizens by American universities in the 1972-1973 school year, and W of these doctorates were granted to women. The total of such doctorates in the 1986-1987 school year was 362, and w of these were granted to women. If the number of doctorates in mathematics granted to female citizens of the United States by American universities decreased from the 1972-1973 school year to the 1986-1987 school year, was the decrease less than 10 percent?
(A) 1/10 (B) W = w + 5

1. statement (A) alone is sufficient but statement (B) alone is not
2. statement (B) alone is sufficient but statement (A) alone is not
3. both (A) and (B) together are sufficient but none of them alone is sufficient
4. both statements are sufficient independently
5. both (A) and (B) together are not sufficient

4) If a bottle is to be selected at random from a certain collection of bottles, what is the probability that the bottle will be defective?
(A) The ratio of the number of bottles in the collection that are defective to the number that are not defective is 3:500.
(B) The collection contains 3,521 bottles.

1. statement (A) alone is sufficient but statement (B) alone is not
2. statement (B) alone is sufficient but statement (A) alone is not
3. both (A) and (B) together are sufficient but none of them alone is sufficient
4. both statements are sufficient independently
5. both (A) and (B) together are not sufficient

Q 1) Is E the ans for Q 1?
554

Awesome Dopa...you got all of them right :D.....yes sure i will post only the questions from now on....Dopa can you please share with us the explanations for these questions...it will be very helpful

555


a few more :)



As you already know the questions, I am just posting the explanations -

1. 0.2h6. what is the value of d, rounded to the nearest tenth ?
Tenths digit is the 1st digit after decimal.

Option - A : d d Option - B : h d could be 0.206,0.216,0.226,0.236,0.246. When rounded to tenths place all of them will become 0.2 i.e. d = 0.2 Sufficient.
Answer is D.
2. If X is an integer, is (X + p) (X + q) an even integer ? Please note that its not given that X is odd or even. And for being able to find if If (X + p) (X + q) is even or odd we have to know about X.

Option - A : q is an even integer. There is no info about X and q. Not sufficient.
Option - B : p is an even integer. There is no info about X and p. Not sufficient.
Option A and B : Both p and q are even but there is no info about X. Not sufficient.
Answer is E.

3. W women in 774 doctorates in 1972-1973; w women in 362 doctorates in 1986-1987. W > w.
was the decrease less than 10 percent ? i.e. is 100(W-w)/W
Option - A : 1/10 77.4 Option - B : W = w + 5 => W - w = 5. For calculating the % decrease, we need to know value of W and thats not known. Not sufficient.
Option A and B : Try to put W as 78 and 85 in the formula written above for calculating % decrease and for both values of W it will be less than 10%. Sufficent.
Answer is C.
4. what is the probability that the bottle will be defective ? Suppose the total bottles are T and defective bottles are t. The probability that the chosen bottle will be defective is t/T or its simplified ratio.

Option - A: The ratio of the number of bottles in the collection that are defective to the number that are not defective is 3:500 => t/(T-t) = 3/500 => (T-t)/t = 500/3 => T/t - 1 = 500/3 => T/t = 503/3 => t/T = 3/503.
Hence, the probability that the bottle will be defective = 3/503. Sufficient.
Option - B : The collection contains 3,521 bottles. No. of Defective/Non defective bottles are unknown. Not sufficient.
Answer is A.

Hope it helps
556

Here are some more :)

1 )

What are the speeds of two trains 80 m and 85 m long respectively?
(A) They take 37.5 seconds to pass each other when they are both running in the same direction
(B) They take 7.5 seconds to pass each other running in opposite directions


2)

Who gets the minimum amount if Rs 385. is divided among A, B and C?
(A) B gets 3/11th of what A and C receive together
(B) A received 2/9th of what B and C receive together


3)


What are the two positive numbers?
(A) Their geometric mean is equal to their arithmetic mean
(B) Their geometric mean is greater than their arithmetic mean by 1.5


4)


How many people heard the chairman's threat?
(A) The chairman threatened 3 employees each of whom repeated it to 4 friends who did not repeat it to any one else for the fear of persecution
(B) No one heard the threat twice


Please provide the answers with explanation...thanks in advance

557
Here are some more :)
1 )What are the speeds of two trains 80 m and 85 m long respectively?
(A) They take 37.5 seconds to pass each other when they are both running in the same direction
(B) They take 7.5 seconds to pass each other running in opposite directions
2)Who gets the minimum amount if Rs 385. is divided among A, B and C?
(A) B gets 3/11th of what A and C receive together
(B) A received 2/9th of what B and C receive together
3)What are the two positive numbers?
(A) Their geometric mean is equal to their arithmetic mean
(B) Their geometric mean is greater than their arithmetic mean by 1.5
4) How many people heard the chairman's threat?
(A) The chairman threatened 3 employees each of whom repeated it to 4 friends who did not repeat it to any one else for the fear of persecution
(B) No one heard the threat twice

Please provide the answers with explanation...thanks in advance

Here are my answers -
1.C
2.C
3.E
4.C

Are these the OAs ?
558
As you already know the questions, I am just posting the explanations -

1. 0.2h6. what is the value of d, rounded to the nearest tenth ?
Tenths digit is the 1st digit after decimal.

Option - A : d d Option - B : h d could be 0.206,0.216,0.226,0.236,0.246. When rounded to tenths place all of them will become 0.2 i.e. d = 0.2 Sufficient.
Answer is D.
2. If X is an integer, is (X + p) (X + q) an even integer ? Please note that its not given that X is odd or even. And for being able to find if If (X + p) (X + q) is even or odd we have to know about X.

Option - A : q is an even integer. There is no info about X and q. Not sufficient.
Option - B : p is an even integer. There is no info about X and p. Not sufficient.
Option A and B : Both p and q are even but there is no info about X. Not sufficient.
Answer is E.

3. W women in 774 doctorates in 1972-1973; w women in 362 doctorates in 1986-1987. W > w.
was the decrease less than 10 percent ? i.e. is 100(W-w)/W
Option - A : 1/10 77.4 Option - B : W = w + 5 => W - w = 5. For calculating the % decrease, we need to know value of W and thats not known. Not sufficient.
Option A and B : Try to put W as 78 and 85 in the formula written above for calculating % decrease and for both values of W it will be less than 10%. Sufficent.
Answer is C.
4. what is the probability that the bottle will be defective ? Suppose the total bottles are T and defective bottles are t. The probability that the chosen bottle will be defective is t/T or its simplified ratio.

Option - A: The ratio of the number of bottles in the collection that are defective to the number that are not defective is 3:500 => t/(T-t) = 3/500 => (T-t)/t = 500/3 => T/t - 1 = 500/3 => T/t = 503/3 => t/T = 3/503.
Hence, the probability that the bottle will be defective = 3/503. Sufficient.
Option - B : The collection contains 3,521 bottles. No. of Defective/Non defective bottles are unknown. Not sufficient.
Answer is A.

Hope it helps

excellent dopa!!need a small help.....
i hvbeen preparing for over a month n hv foud tht DS is one of the area where i need to wrk. I hv done OG n need more practice in DS. Kindly suggest alternative stuff for good practice n breaking this DS jinx.
The problem is tht i seem to be solving them correctly bt am not confidentunless i see answers to them.

so plz plz plz help
559

[
Quote:
Originally Posted by naveen_petrucci View Post
Here are some more :smile:
1 )What are the speeds of two trains 80 m and 85 m long respectively?
(A) They take 37.5 seconds to pass each other when they are both running in the same direction
(B) They take 7.5 seconds to pass each other running in opposite directions
2)Who gets the minimum amount if Rs 385. is divided among A, B and C?
(A) B gets 3/11th of what A and C receive together
(B) A received 2/9th of what B and C receive together
3)What are the two positive numbers?
(A) Their geometric mean is equal to their arithmetic mean
(B) Their geometric mean is greater than their arithmetic mean by 1.5
4) How many people heard the chairman's threat?
(A) The chairman threatened 3 employees each of whom repeated it to 4 friends who did not repeat it to any one else for the fear of persecution
(B) No one heard the threat twice

Please provide the answers with explanation...thanks in advance

Here are my answers -
1.C
2.C
3.E
4.C

Are these the OAs ?

I guess the answer should be -

1.C
2.C
3.E
4.A

For the last question ( where i differ from Dopa):
irrespective of whether i have heared it once or twice , we have to caluculate number of persons who heard about the threat and that we can get from first statement alone.
hope m not making a mistake in understanding the problem

560

We can eliminate the "too obvious" answers in harder DS qns... We need to think logically what a normal test taker would choose on a hard qn and choose the opposite of it...

I am able to get most of the hard DS qns right using this technique...

Question is ...
In REAL GMAT when will the harder DS qns start to appear?
In what qn range?
my guess is after qn numbers 25 or 28???

Am i right? Please let me know because in easy and intermediate qns if you use this approach you will get a wrong answer for sure.

Many thanks in advance!!
Regards,
Shiva

561
Here are my answers -
1.C
2.C
3.E
4.C

Are these the OAs ?

yup i agree....
but for the 4th ques i feel OA is A.
ur views y u chose C

dear naveen pl post the correct answers