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exponents question --- help!

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exponents question --- help!

by san2009 » Fri May 07, 2010 6:24 am
I came across this question online
Need help!!

If x^3y^4 = 5000, is y = 5?
1) y is a positive integer
2) x is an integer.

My rephrased question is, is x=2? and I find that both statements 1 and 2 together are iunsufficient.
The OA is C though. Pls advise. Thx
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by liferocks » Fri May 07, 2010 6:29 am
5000=2^3*5^4

is the only way to represent as multiple of integer hence if X and Y are integer then x=2 and Y=5

but unless we consider both 1 and 2 it cannot be concluded that x as well as y are integer
..neither of the statements is not sufficient alone
hence ans is C
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by san2009 » Fri May 07, 2010 7:15 am
sorry, dont follow your explanation
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by 2011mbaspirant » Fri May 07, 2010 12:07 pm
Either the question is wrong or the answer us E. The original question transforms to x^12y=5000.
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by liferocks » Fri May 07, 2010 4:56 pm
san2009 wrote:sorry, dont follow your explanation
What i meant is 5000 can be expressed as multiple of a cube and a quadruple in only one way that is cube of 2 and quadruple of 5

so the question reduces to 5000==2^3*5^4 =x^3y^4

but this we can say only when we know that x and y both are integers.

condition 1 says y is an integer but no information about x
similarly condition 2 says x is an integer but no information about y

so either of the conditions is not sufficient to conclude.

together the conditions says that x and y both are integer..hence we can say x=2 and y=5.
foes this clarifies the confusion?
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by debmalya_dutta » Fri May 07, 2010 5:01 pm
So you have interpreted x^3y^4
as x^3 * y^4 and some of us interpreted it as been x ^(3y^4). surely makes life much easier your way .
liferocks wrote:
san2009 wrote:sorry, dont follow your explanation
What i meant is 5000 can be expressed as multiple of a cube and a quadruple in only one way that is cube of 2 and quadruple of 5

so the question reduces to 5000==2^3*5^4 =x^3y^4

but this we can say only when we know that x and y both are integers.

condition 1 says y is an integer but no information about x
similarly condition 2 says x is an integer but no information about y

so either of the conditions is not sufficient to conclude.

together the conditions says that x and y both are integer..hence we can say x=2 and y=5.
foes this clarifies the confusion?
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