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The sum of positive integers x and y is 77, what is the
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29 Jan 2012, 03:34
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Here is the data sufficiency problem from GMATPrep; The sum of positive integers x and y is 77, what is the value of xy? (1) x=y+1 (2) x and y have the same tens digit. I answered the question as A becuase i thought the statement (1) alone was sufficient. GMATPrep on the other hand said that it is a D each statement alone is sufficient. Here is my problem, if we do not know the statement (1), how can we decide these numbers? They of course should be with a tens digit of 3, but all those pairs as (30,37), (31,36), (32,35), (33,34) can maintain the sum of 77, with difference results when they are multiplied. It is because i did not think statement 2 is sufficient, can anyone make it clear, if the GMATPrep's answer is correct? Thanks.
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Re: The sum of positive integers x and y is 77..
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29 Jan 2012, 03:47
Hi , I got the answer as D The sum of positive integers x and y is 77, what is the value of xy? (1) x=y+1 (2) x and y have the same tens digit. Statement A : X=Y+1 so using eqn X+Y=77 2Y+1=77 Y= 38 X= 39 thus we can find the value of XY Hence A is sufficient Statement 2 : Says X & Y have the same 10's digit => X= 10 * A + B & Y = 10 * A + C For X + Y = 77 & the above constraint we can only opt for a number between 30  39 thus the choice of 38 & 39 Hence B is sufficient Thus Answer D
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The sum of positive integers x and y is 77, what is the
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29 Jan 2012, 03:52
ustureci wrote: Here is the data sufficiency problem from GMATPrep;
The sum of positive integers x and y is 77, what is the value of xy?
(1) x=y+1 (2) x and y have the same tens digit.
I answered the question as A becuase i thought the statement (1) alone was sufficient. GMATPrep on the other hand said that it is a D each statement alone is sufficient. Here is my problem, if we do not know the statement (1), how can we decide these numbers? They of course should be with a tens digit of 3, but all those pairs as (30,37), (31,36), (32,35), (33,34) can maintain the sum of 77, with difference results when they are multiplied. It is because i did not think statement 2 is sufficient, can anyone make it clear, if the GMATPrep's answer is correct? Thanks. Welcome to GMAT Club. Hope below solution clears your doubts. The sum of positive integers x and y is 77, what is the value of xy?Given: x+y=77. Question: xy=? (1) x=y+1 > together with x+y=77 we have two distinct linear equations, hence we can solve the for variables and obtain the value of xy. Sufficient. (2) x and y have the same tens digit > x and y cannot have the tens digit of 2 or 4 (as 29+29<77 and 40+40>77) > the units digit is 3 > now, if x=y then x=y=77/2=38.5 > as both are integers then x and y are 38 and 39 or vise versa (neither of them can be less than 38 as in this case the sum will be less than 77: 37+39=76). Therefore xy=38*39. Sufficient. Answer: D. The problem with your solution is that (30,37), (31,36), (32,35), (33,34) add up to 67 not 77. Hope it's clear.
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Re: The sum of positive integers x and y is 77, what is the
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29 Jan 2012, 04:37
sorry for the inconvenience:) it may happen (mistakes in simple math), thanks anyway.



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Re: The sum of positive integers x and y is 77, what is the
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Re: The sum of positive integers x and y is 77, what is the
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02 Feb 2012, 03:28
The sum of positive integers x and y is 77, what is the value of xy? (1) x=y+1 (2) x and y have the same tens digit. Ans: consider the first statement x=y+1 By observation x=39 and y=37 xy=39*38 Hence 1 alone is enough . X and Y have same 10s digit. tens digits have to be 3 only . Only possibility is x,y=(38,39). Both statements alone are sufficient.
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Re: The sum of positive integers x and y is 77, what is the
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30 Jun 2012, 11:58
Is it just me or is it that most questions in GMAT which show A as OK extremely easily(like in this question) will almost always have D as answer....but the second statement will be just a little harder to understand
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