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If a,b,k, and m are positive integers, is a^k a factor of

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If a,b,k, and m are positive integers, is a^k a factor of  [#permalink]

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New post 07 Apr 2011, 23:32
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If a,b,k, and m are positive integers, is a^k a factor of b^m?

1) a is a factor of b

2) k ≤ m

I don't know OA.

OPEN DISCUSSION OF THIS QUESTION IS HERE: if-a-b-k-and-m-are-positive-integers-is-a-k-a-factor-of-88503.html

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Re: If a,b,k, and m are positive integers, is a^k a factor of  [#permalink]

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New post 07 Apr 2011, 23:54
Baten80 wrote:
If a,b,k, and m are positive integers, is a^k a factor of b^m?

1) a is a factor of b

2) k ≤ m

I don't know OA.


we need to find out if \(\frac{b^m}{a^k}\) is an integer.

Statement 1 says a is a factor of b so \(b = na\) where n is an integer.

So \(\frac{b^m}{a^k}\) = \(\frac{(na)^m}{a^k}\) = \(\frac{(n^m*a^m)}{a^k}\)

This will be integer if \(a^m \geq a^k\) which will happen only if \(k \leq m\)which is not given in statement 1, so insufficient

Statement 2 doesnt say anything about a and b so insufficient

Combining statement 1 and 2 we can answer the question in affirmative, hence sufficient and Answer is C.
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Re: If a,b,k, and m are positive integers, is a^k a factor of  [#permalink]

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New post 08 Apr 2011, 00:33
Is b^m = r *a^k ? (where p is as an integer)

(1) b = p * a (where p is as an integer)

so b^k = p^k * a^k

but we don't know the relationship between m and k, so insufficient.

e.g. a = 3, b = 6

so 6^2/3^3 is not an integer.

(2) No information about a and b, so insufficient.

(1) and (2) => b^m = p^k * a^k or, b^m/a^k = p^k (an integer), so sufficient

Answer - C
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Re: If a,b,k, and m are positive integers, is a^k a factor of  [#permalink]

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New post 08 Apr 2011, 18:22
My Answer is C too.

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Re: If a,b,k, and m are positive integers, is a^k a factor of  [#permalink]

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New post 08 Apr 2011, 20:22
Take a = 2, b = 6
=>2^k and 6^m
=>2^k and 2^m x 3^m
If k<=m, for any positive value of k and m, 2^k is always a factor of 2^m
So C
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Re: If a,b,k, and m are positive integers, is a^k a factor of  [#permalink]

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New post 12 Sep 2016, 11:48
Baten80 wrote:
If a,b,k, and m are positive integers, is a^k a factor of b^m?

1) a is a factor of b

2) k ≤ m

I don't know OA.



1) b^m = a^k * n. Since a is factor of B, let a =2, b=8
so 2^3m = 2^k * n. 2^k can only be a factor of 2^3m if the exponents of 2^k is less than 2^3m for all k and m. So not sufficient

2)k <= m, not sufficient because a and b relationship not given. If a = 3, b = 5, can be yes or no for a^k a factor of b^m

1+2) given a is a factor of b and the exponent of a will be smaller than or equal to the exponent of b, a^k is then a factor of b^m. C
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Re: If a,b,k, and m are positive integers, is a^k a factor of  [#permalink]

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New post 14 Aug 2017, 06:25
Baten80 wrote:
If a,b,k, and m are positive integers, is a^k a factor of b^m?

1) a is a factor of b

2) k ≤ m

I don't know OA.


Question: is \(a^k\) a factor of \(b^m\) --> \(a^kx=b^m\), where \(x\) is an integer? --> \(x=\frac{b^m}{a^k}\). So basically the question is: Is \(x\) an integer \(>0\)?

(1) \(a\) is a factor of \(b\) --> \(ay=b\) --> \(x=\frac{a^my^m}{a^k}\) --> \(x=a^{m-k}y^m\). Now if \(m<k\) and \(a\) is not a factor of \(y\), then \(x\) will not be an integer. Not sufficient.

Or even without any algebra: if a and b are equal to say 3 and m<k (there are less b's than a's) then a^k won't be a factor of b^m. Though if k<=m then even if a and b are not equal still a^k will be a factor of b^m as there will be enough b's for a's.

(2) \(k\leq{m}\), not sufficient on it's own.

(1)+(2) \(x=a^{m-k}y^m\) and \(k<m\), hence \(x\) is an integer. Sufficient. (Or again as there are more b's then a's (enough b's for a) then a^k is a factor of b^m, for example (bbb)/(aa))

Answer: C.

OPEN DISCUSSION OF THIS QUESTION IS HERE: if-a-b-k-and-m-are-positive-integers-is-a-k-a-factor-of-88503.html

--== Message from the GMAT Club Team ==--

THERE IS LIKELY A BETTER DISCUSSION OF THIS EXACT QUESTION.
This discussion does not meet community quality standards. It has been retired.


If you would like to discuss this question please re-post it in the respective forum. Thank you!

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Re: If a,b,k, and m are positive integers, is a^k a factor of   [#permalink] 14 Aug 2017, 06:25
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