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# If 2^m = 5 and 5^n = 3, then 3^(1/n)/2^

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CEO
Joined: 12 Sep 2015
Posts: 2889
If 2^m = 5 and 5^n = 3, then 3^(1/n)/2^  [#permalink]

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12 Feb 2017, 07:47
1
Top Contributor
1
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Difficulty:

35% (medium)

Question Stats:

71% (01:27) correct 29% (02:21) wrong based on 139 sessions

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If $$2^m= 5$$ and $$5^{1/n} = 3$$, then $$\frac{3^n}{2^{-2m}}$$ =

A) 1/25
B) 1/5
C) 5
D) 25
E) 125

* kudos for all correct solutions

EDIT: Sorry - wrong forum

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Brent Hanneson – GMATPrepNow.com

Math Expert
Joined: 02 Aug 2009
Posts: 6802
Re: If 2^m = 5 and 5^n = 3, then 3^(1/n)/2^  [#permalink]

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12 Feb 2017, 09:38
1
GMATPrepNow wrote:
If $$2^m= 5$$ and $$5^{1/n} = 3$$, then $$\frac{3^n}{2^{-2m}}$$ =

A) 1/25
B) 1/5
C) 5
D) 25
E) 125

* kudos for all correct solutions

EDIT: Sorry - wrong forum

Hi,
Let's convert the equations given to fit into $$\frac{3^n}{2^{-2m}}$$ ..

$$2^m= 5, ..... 2^{2m}=5^2=25$$ and $$5^{1/n} = 3......(5^{1/n})^n=3^n.....3^n=5$$...

$$\frac{3^n}{2^{-2m}}=3^n*2^{2m}$$ ..
Substitute the values in $$3^n*2^{2m}=5*25=125$$

E
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1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

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CEO
Joined: 12 Sep 2015
Posts: 2889
Re: If 2^m = 5 and 5^n = 3, then 3^(1/n)/2^  [#permalink]

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12 Feb 2017, 09:53
Top Contributor
GMATPrepNow wrote:
If $$2^m= 5$$ and $$5^{1/n} = 3$$, then $$\frac{3^n}{2^{-2m}}$$ =

A) 1/25
B) 1/5
C) 5
D) 25
E) 125

Given: $$2^m= 5$$
We need to determine the value of $$2^{-2m}$$
So, take $$2^m= 5$$ and raise both sides to the power of -2
We get: (2^m)^(-2) = 5^(-2)
Apply Power of a Power rule to get: 2^(-2m) = 5^(-2)

Given: $$5^{1/n} = 3$$
We need to determine the value of 3^n
So, take $$5^{1/n} = 3$$ and raise both sides to the power of n
We get: [5^(1/n)]^n = 3^n
Apply Power of a Power rule to get: 5^1 = 3^n

So, (3^n)/2^(-2m) = (5^1)/[(5^(-2)]
= 5^3
= 125

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Brent Hanneson – GMATPrepNow.com

Re: If 2^m = 5 and 5^n = 3, then 3^(1/n)/2^ &nbs [#permalink] 12 Feb 2017, 09:53
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