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# 2^x = 7, then 2^2x =? a)49 b)7 c)128 d)64 e)32 Please assist with a

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Manager
Joined: 13 Sep 2016
Posts: 115
GMAT 1: 800 Q51 V51
2^x = 7, then 2^2x =? a)49 b)7 c)128 d)64 e)32 Please assist with a  [#permalink]

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29 Sep 2016, 09:40
5
00:00

Difficulty:

15% (low)

Question Stats:

75% (00:49) correct 25% (01:26) wrong based on 101 sessions

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2^x = 7, then 2^2x =?

A) 49
B) 7
C) 128
D) 64
E) 32

Magoosh GMAT Instructor
Joined: 28 Dec 2011
Posts: 4472
2^x = 7, then 2^2x =? a)49 b)7 c)128 d)64 e)32 Please assist with a  [#permalink]

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29 Sep 2016, 10:23
2
1
alanforde800Maximus wrote:
2^x = 7, then 2^2x =?

A) 49
B) 7
C) 128
D) 64
E) 32

Dear alanforde800Maximus,

I'm happy to respond.

Here, we have to be comfortable with the laws of exponents. For example, A^(pq) = (A^p)^q. That's a very important patterns to know.

Here, 2^(2x) can be rewritten as (2^x)^2. Since, we know that 2^x = 7, we know that (2^x)^2 = 49. Answer = (A).

Here are some GMAT Math Flashcards you might find helpful.

Does this make sense?
Mike
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Mike McGarry
Magoosh Test Prep

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Re: 2^x = 7, then 2^2x =? a)49 b)7 c)128 d)64 e)32 Please assist with a  [#permalink]

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27 Feb 2017, 04:42
2^2x = 2^x * 2^x = 7*7 = 49
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Re: 2^x = 7, then 2^2x =? a)49 b)7 c)128 d)64 e)32 Please assist with a  [#permalink]

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18 Oct 2018, 21:20
For this question

$$2^x = 7$$

We have to find (2)^2x

Now we can write 2^2x as $$(2^x)^2$$

Which will imply $$7^2$$

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Re: 2^x = 7, then 2^2x =? a)49 b)7 c)128 d)64 e)32 Please assist with a   [#permalink] 18 Oct 2018, 21:20
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