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What is the value of 2^a*4^b?

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Bunuel
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What is the value of 2^a*4^b? [#permalink] New post   04 Nov 2014, 09:47
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A
B
C
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E

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76% (00:51) correct 24% (00:54) wrong based on 271 sessions
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Tough and Tricky questions: Exponents.



What is the value of 2^a*4^b?

(1) a = -2b
(2) b = 4

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A
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2013gmat
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Re: What is the value of 2^a*4^b? [#permalink] New post   04 Nov 2014, 23:33
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1) a= -2b

2^(-2b) 4^b = 1/4^b * 4^b = 1

sufficient.

2) b=4

we don't know the value of a, thus insufficient.

Thus, A.

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Re: What is the value of 2^a*4^b? [#permalink] New post   05 Nov 2014, 00:09
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We have: \(2^a*4^b = 2^a*2^2b = 2^(a+2b)\)

S1: \(a = -2b --> a + 2b = 0\)
--> \(2^0 = 1\)
SUFF

S2: \(b = 4\)
NOT SUFF because we don't know a.

Ans: A
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Re: What is the value of 2^a*4^b? [#permalink] New post   05 Nov 2014, 21:34
2^a*4^b = 2^(a+2b) = ?

Statement 1 : a = -2b => a+2b =0
Therefore 2^(a+2b) = 2^0 =1

Statement 2: b = 4. Clearly insufficient
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What is the value of 2^a4^b? [#permalink] New post   05 Jun 2016, 05:08
What is the value of \(2^a\)\(4^b\)?

(1) a = -2b

(2) b = 4
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Re: What is the value of 2^a*4^b? [#permalink] New post   05 Jun 2016, 05:13
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AbdurRakib wrote:
What is the value of \(2^a\)\(4^b\)?

(1) a = -2b

(2) b = 4


Merging topics. Please refer to the discussion above.
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Re: What is the value of 2^a*4^b? [#permalink] New post   12 Jun 2016, 05:08
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Bunuel wrote:

Tough and Tricky questions: Exponents.



What is the value of 2^a*4^b?

(1) a = -2b
(2) b = 4

Kudos for a correct solution.


Question stem is \(2^a * 4^b = ?\)

(1) \(a=-2b\)

Put this in given stem

\(2^{-2b} * 4^b =\frac{1}{2^{2b}} * 4^b=\frac{1}{4^b} * 4^b= 1\) --- this is Sufficient to answer. Hence option \(B\), \(C\) and \(E\) are ruled out.

(2) \(b =4\) --- This is clearly not sufficient to answer as we don't know the value of \(a\). --- hence option \(D\) is ruled out.

The only option remain is \(A\).

Correct Answer \(A\)
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Re: What is the value of 2^a*4^b? [#permalink] New post   12 May 2019, 10:12
From Statement 1:
2^a= 2^-2b= 4^-b= 1/4^b
So, (1/4^b)*4^b= 1
Sufficient
From statement 2: we only know B's value. Hence insufficient.
IMO A

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Re: What is the value of 2^a*4^b? [#permalink] New post   16 May 2022, 23:55
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Re: What is the value of 2^a*4^b? [#permalink]
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