Data Sufficiency

I got this one wrong - Can someone help me out by solving this

debmalya_dutta wrote:I got this one wrong - Can someone help me out by solving this

X/Y = 7

assume total of 80+N people.
70 buy X
10 buy Y.
N buy neither

Percentage of y = 10/(80+N) *100
=1000/80+N

27 percent of (80+N) purchase neither x nor y. = N
which means N can be calculated.
hence percentage of Y can be calculated.
SUFF

70 percent purchase both x and y
We have no info about how manybuy neither. Hence we do not know the total number of people.
Therefore, percentage cannot be calculated.
INSUFF

pick A.

Whats the OA?

thanks Mate...I had picked A and I was so dead sure that I thought that I must be missing some aspect of the question.. per Kaplan (the GMAT test 2) , the answer is C...

Hey..try the other one I just posted..I think I incorrectly posted it within DS... But take a look..I got that wrong too.. I am not sure why?

debmalya_dutta wrote:thanks Mate...I had picked A and I was so dead sure that I thought that I must be missing some aspect of the question.. per Kaplan (the GMAT test 2) , the answer is C...

Hey..try the other one I just posted..I think I incorrectly posted it within DS... But take a look..I got that wrong too.. I am not sure why?

Think this way..

What about people who buy both X and Y.

so, you can't say that Xonly+ Yonly+ both +N =100

do you know Xonly or Yonly ? no.. so A can't be the answer.

x2suresh wrote:

debmalya_dutta wrote:thanks Mate...I had picked A and I was so dead sure that I thought that I must be missing some aspect of the question.. per Kaplan (the GMAT test 2) , the answer is C...

Hey..try the other one I just posted..I think I incorrectly posted it within DS... But take a look..I got that wrong too.. I am not sure why?

Think this way..

What about people who buy both X and Y.

so, you can't say that Xonly+ Yonly+ both +N =100

do you know Xonly or Yonly ? no.. so A can't be the answer.

Dont think I need to know Xonly or Yonly etc... In the question asks for Y (doesnt make any distinction between Y only vs Y &X)... The question is what % of population purchase Newspaper Y ... It doesnt ask for % of population purchasing only Newspaper Y

I see why the answer is C now. Let me re-write my post.

X/Y = 7

assume total of 80+N people.
70 buy X. 70 - B buy only X
10 buy Y. 10 - B buy only Y
B buy both.
N buy neither

Total y = only Y + B
= 10 - B + B


Total = only X + only Y + both + neither
Total = 70 - B + 10 - B + B + N
Total = 70 - B + total Y + N
Total - N - 70 + B = total Y
Hence we need both B and N to find the percentage of Y

27 percent of (80+N) purchase neither x nor y. = N
which means N can be calculated.
But still we are unknown about B.
INSUFF

70 percent purchase both x and y
only B is given. we need N too.
INSUFF

Combining, we get both B and N.
pick C.

kvcpk wrote:I see why the answer is C now. Let me re-write my post.

X/Y = 7

assume total of 80+N people.
70 buy X. 70 - B buy only X
10 buy Y. 10 - B buy only Y
B buy both.
N buy neither

Total y = only Y + B
= 10 - B + B


Total = only X + only Y + both + neither
Total = 70 - B + 10 - B + B + N
Total = 70 - B + total Y + N
Total - N - 70 + B = total Y
Hence we need both B and N to find the percentage of Y

27 percent of (80+N) purchase neither x nor y. = N
which means N can be calculated.
But still we are unknown about B.
INSUFF

70 percent purchase both x and y
only B is given. we need N too.
INSUFF

Combining, we get both B and N.
pick C.

thanks ...

@x2suresh
You were right.. Oversight at my end..Thanks