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Intern
Joined: 21 Jan 2007
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full length gmattest: difficult questions.. [#permalink]
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07 Mar 2007, 02:31
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Hi to all, I did the full length GmatTest provided here on gmatclub and found different solutions for these 3 questions... i am not entirely convinced by the OA, which are the ones in bold.
Could u enlighten me ?? (my answers are those in cursive)
Thanks a lot
Riccardo
27. If x and y are positive integers, is x > y?
(1) (x)(x) < y
(2) The square root of x is less than y
(A) statement 1 alone is sufficient to answer the question, but statement 2 alone is not sufficient
(B) statement 2 alone is sufficient to answer the question, but statement 1 alone is not sufficient
(C) both statements together are needed to answer the question, but neither statement alone is sufficient
(D) either statement by itself is sufficient to answer the question
(E) not enough facts are given to answer the question
28. Machine M can produce x units in 3/4 of the time it takes machine N to produce x units. Machine N can produce x units in 2/3 the time it takes machine O to produce x units. If all three machines are working simultaneously, what fraction of the total output is produced by machine N?
(A) 1/2
(B) 1/3
(C) 4/13
(D) 8/29
(E) 6/33
32. Charmaine spent 2/5 of her income in January for rent, and 3/4 of the remainder on other expenses. If she put the remaining $180 in her savings account, how much was her income in January?
(A) $1,000
(B) $1,200
(C) $1,400
(D) $1,600
(E) $1,800



Manager
Joined: 09 Jan 2007
Posts: 240

27.
(E) is right answer.
Lets assume x=4 and y=9
1) x^2=16, which is greater than y. So not sufficient
2) sqrt(x) = +/2 < y
Now if x= 1 and y = 1, the results does not match.



Manager
Joined: 09 Jan 2007
Posts: 240

Mâ€™s production : 3/4t>1 => t>4/3
Nâ€™s production : t>1
Oâ€™s production : 3/2t>1 =>t>2/3
If 3 m/c work simultaneously total production in time t > 1+4/3+2/3 = (3+4+2)/3 = 3
So, N produces 1/3, which is (B)



Manager
Joined: 09 Jan 2007
Posts: 240

32.
Lets assume total income is 1
Rent = 2/5
Remains = 12/5 = 3/5
Other expenses = 3/5*3/4 = 9/20
Remains = 3/59/20=3/20
3/20 part of income = 180
1 part = 180*20/3 = 1200
So the answer is (B)



Senior Manager
Joined: 29 Jan 2007
Posts: 441
Location: Earth

27) A
rdg,
For 27, stmt 1 what you are given is X*X < Y, you are taking values to contradict the given condition itself
my reasoning was if X*X, which is always positive, is less than Y then X has to be less than Y. e.g X =  3 or +3 if Y is greater than X * X which is 9 then both X values are less than Y. So Stmt one is suff.
Stmt 2 however is not suff. take X = 9 and Y = 2
here sqrt X is 3 or +3 one of which is less than Y and other is greater than Y.
28)  B
as rdg exaplained
32)  B
as rdg explained



Manager
Joined: 09 Jan 2007
Posts: 240

Assume x=2, and y=9.
now x^2 is still <y.
Therefore, I meant the statement 1 is not sufficient.
Last edited by rdg on 07 Mar 2007, 22:56, edited 1 time in total.



Senior Manager
Joined: 29 Jan 2007
Posts: 441
Location: Earth

rdg,
I think you are daling with it incorrectly.
Try reading it like this...
if (X*X) < Y is true then
Can we answer if X > Y?
And answer is YES, WE CAN ANSWER THE QUESTION. although the answer would be NO as X will always be less than Y id (X*X) < Y
Last edited by kyatin on 07 Mar 2007, 23:24, edited 1 time in total.



Director
Joined: 13 Dec 2006
Posts: 510
Location: Indonesia

Dear rdg,
I am not convinced with the explanation for question number 27. In my opinion following should be the explanation:
Answer A is correct.
Prob: To find out whether x>y
condition 1) : x.x<y>9 as the given condition is X.X<Y>3, which means x<y. So condition one is sufficient to solve the problem.
Now lets see condition 2), which say sqrtX<y> 2, where it can take values such as 3,4,5,6......so on... since sqrt X is 2, X will be 4.
So if Y = 3, then we can say that X>Y, but for Y=5, X<Y.
Hence statement 2 is not sufficient.
Now since statement 1 is sufficient but statement 2 is not sufficient our answer will be A.
kindly correct me if I am wrong...
Regards
Amardeep










