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If x and y are positive integers and x^4 + y^4 < 10,000, then the grea [#permalink]
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24 May 2011, 06:55
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If x and y are positive integers and x^4 + y^4 < 10,000, then the greatest possible value of x is between (A) 0 and 3 (B) 3 and 6 (C) 6 and 9 (D) 9 and 12 (E) 12 and 15 == Message from GMAT Club Team == This is not a quality discussion. It has been retired. If you would like to discuss this question please repost it in the respective forum. Thank you! To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative  Verbal Please note  we may remove posts that do not follow our posting guidelines. Thank you.



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Re: If x and y are positive integers and x^4 + y^4 < 10,000, then the grea [#permalink]
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24 May 2011, 08:13
dreambeliever wrote: If x and y are positive integers and x^4 + y^4< 10,000, then the greatest possible value of x is between (A) 0 and 3 (B) 3 and 6 (C) 6 and 9 (D) 9 and 12 (E) 12 and 15 TO make X as big as possible, y^4 must be small. So if y = 1 then the equation is x^4 + 1 < 10,000 or x^4 + 1 < 10 ^ 4 So you know x must be less than 10. So option C is best answer.



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Re: If x and y are positive integers and x^4 + y^4 < 10,000, then the grea [#permalink]
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24 May 2011, 22:20
I answered, D
x^4 + y^4 < 10,000 set y=1 x^4 < 9,999
10^4 = 10,000
so, x=9



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Re: If x and y are positive integers and x^4 + y^4 < 10,000, then the grea [#permalink]
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25 May 2011, 06:29
Where is this from ? Looks like a modified version of this question. x4y4gmatprep98713.html
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Re: If x and y are positive integers and x^4 + y^4 < 10,000, then the grea [#permalink]
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Updated on: 25 May 2011, 10:50
Step 1: x^4+y^4<10,000
x^4 will be maximum when y^4 is minimum. y^4 is minimum when y=1 because y should be a positive integer.
Step 2:
x^4+1^4<10,000 => x^4+1<10,000 =>x^4<10,0001 =>x^4<9,999
Lets substitute x=10, i.e 10*10*10*10 = 10,000
So the value of x should be less than 10 i.e 8. It can't be 9 because no answer choice has 9.
So the answer is option (C)
Originally posted by mba4viplav on 25 May 2011, 06:47.
Last edited by mba4viplav on 25 May 2011, 10:50, edited 1 time in total.



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Re: If x and y are positive integers and x^4 + y^4 < 10,000, then the grea [#permalink]
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25 May 2011, 07:08
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to the two people who picked D is the answer. We both did the work the same way. We agree x < 10.
So why D?
D claims that x can be 9,10,11,12. Which it can't be. So unless I am misunderstanding something, I will stick with my answer of C which says x must be less than 10



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Re: If x and y are positive integers and x^4 + y^4 < 10,000, then the grea [#permalink]
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25 May 2011, 07:51
Seems some problem with the question especially RHS. x and y being positive integers y #0 and other values of x do not give an integer y value other than x=0. Hence the question needs to be checked.
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Re: If x and y are positive integers and x^4 + y^4 < 10,000, then the grea [#permalink]
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25 May 2011, 15:13
The question is from Jeff Sackmann's challenge series. I think OA provided was D which is why I posted it here. I agree that the and should be C.
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Re: If x and y are positive integers and x^4 + y^4 < 10,000, then the grea [#permalink]
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25 May 2011, 20:17
dreambeliever wrote: If x and y are positive integers and x^4 + y^4< 10,000, then the greatest possible value of x is between (A) 0 and 3 (B) 3 and 6 (C) 6 and 9 (D) 9 and 12 (E) 12 and 15 If it is "inclusive": C and D both are the answers. If it is "exclusive": None of the above.
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