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If (3^a)*(4^b)=c , then what is the value of b? 1. 5^a=25 2.

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If (3^a)*(4^b)=c , then what is the value of b? 1. 5^a=25 2. [#permalink] New post 18 Jun 2006, 04:14
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If (3^a)*(4^b)=c , then what is the value of b?

1. 5^a=25
2. c=36

**Edited :oops:

Last edited by GMATT73 on 18 Jun 2006, 15:07, edited 1 time in total.
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 [#permalink] New post 18 Jun 2006, 04:31
shobhitb wrote:
straight B for me


Can you please illustrate how you got that answer?
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 [#permalink] New post 18 Jun 2006, 05:32
GMATT73 wrote:
shobhitb wrote:
straight B for me


Can you please illustrate how you got that answer?


Statement 1

a=2 but no value of b so cannot determine c

Statement 2

c is given!

So sufficient
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 [#permalink] New post 18 Jun 2006, 06:56
(B) was my guess too, but according to the OA we are both wrong.
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 [#permalink] New post 18 Jun 2006, 07:04
what is the source of this problem, Matt?!!
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Re: DS Algebra [#permalink] New post 18 Jun 2006, 07:28
GMATT73 wrote:
If (3^a)*(4^b)=c , then what is the value of c?

1. 5^a=25
2. c=36

maybe some typo?
I guess if it is not B than it should be D.C is out cause 2st alone is sufficient
So How did they get the valuse of C from 1st?
All we can get from 5^a=25 is that a=2
9*4^b=c defenitely not suff

Matt but the question was what is the value of C ))) I knew there was a typo)) :wink:
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Last edited by Yurik79 on 19 Jun 2006, 08:41, edited 1 time in total.
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 [#permalink] New post 18 Jun 2006, 09:06
Matt,

It doesn't seem right. It probably has to be something like (C < 36) or ( C > 36) or something else. I mean, if it says C = 36, then (B) certainly qualifies.
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 [#permalink] New post 18 Jun 2006, 15:05
Here`s the problem in source format.
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 [#permalink] New post 18 Jun 2006, 21:30
GMATT73,
Can you post the Kaplan explanation for this.

Are there any fraction values of a/b that can also yield 36.
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 [#permalink] New post 18 Jun 2006, 23:11
St1:

No information about c. Insufficient.

St2:
c = 36, (3^a)(4^b) = c

Can be 9*4 --> a = 2, b = 1.

I'll go with B. I can't think of any other combination that works.
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 [#permalink] New post 19 Jun 2006, 05:22
Well, I suppose since the stem didn't say a and b are integers, we really can't say that a=2 and b=1 if c=36. For example, a could equal to (ln4/ln3+2) and b could equal to 0. (I had chosen B too, and looks like it IS wrong.)
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Last edited by HongHu on 19 Jun 2006, 07:28, edited 1 time in total.
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 [#permalink] New post 19 Jun 2006, 06:01
sgrover wrote:
GMATT73,
Can you post the Kaplan explanation for this.

Are there any fraction values of a/b that can also yield 36.


Here is the OE from Kaplan. Not that it helps much...
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 [#permalink] New post 19 Jun 2006, 06:27
The correct answer is C (also in Kaplan as the link provided by you) ;)

If (3^a)*(4^b)=c , then what is the value of b?

1. 5^a=25
2. c=36

1. 5^a= 25 --> a= 2 , nothing about c ---> insuff
2. nothing about a --> insuff

1 and 2:
a=2 ---> 3^a = 9, we have c=36 ---> 4^b = 36/9= 4 --> b=1
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 [#permalink] New post 19 Jun 2006, 06:34
laxieqv wrote:
The correct answer is C (also in Kaplan as the link provided by you) ;)

If (3^a)*(4^b)=c , then what is the value of b?

1. 5^a=25
2. c=36

1. 5^a= 25 --> a= 2 , nothing about c ---> insuff
2. nothing about a --> insuff

1 and 2:
a=2 ---> 3^a = 9, we have c=36 ---> 4^b = 36/9= 4 --> b=1


Here`s where I get a little hazy....

If (3^a)*(4^b)=36, then doesn`t b have to equal 1?
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 [#permalink] New post 19 Jun 2006, 06:49
GMATT73 wrote:
laxieqv wrote:
The correct answer is C (also in Kaplan as the link provided by you) ;)

If (3^a)*(4^b)=c , then what is the value of b?

1. 5^a=25
2. c=36

1. 5^a= 25 --> a= 2 , nothing about c ---> insuff
2. nothing about a --> insuff

1 and 2:
a=2 ---> 3^a = 9, we have c=36 ---> 4^b = 36/9= 4 --> b=1


Here`s where I get a little hazy....

If (3^a)*(4^b)=36, then doesn`t b have to equal 1?


if we know only c ..it's impossible to conclude that b=1 coz a and b are not necessarily integers :)
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 [#permalink] New post 19 Jun 2006, 06:57
laxieqv wrote:
GMATT73 wrote:
laxieqv wrote:
The correct answer is C (also in Kaplan as the link provided by you) ;)

If (3^a)*(4^b)=c , then what is the value of b?

1. 5^a=25
2. c=36

1. 5^a= 25 --> a= 2 , nothing about c ---> insuff
2. nothing about a --> insuff

1 and 2:
a=2 ---> 3^a = 9, we have c=36 ---> 4^b = 36/9= 4 --> b=1


Here`s where I get a little hazy....

If (3^a)*(4^b)=36, then doesn`t b have to equal 1?


if we know only c ..it's impossible to conclude that b=1 coz a and b are not necessarily integers :)


DUH!

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 [#permalink] New post 21 Jun 2006, 08:17
laxieqv wrote:
GMATT73 wrote:
laxieqv wrote:
The correct answer is C (also in Kaplan as the link provided by you) ;)

If (3^a)*(4^b)=c , then what is the value of b?

1. 5^a=25
2. c=36

1. 5^a= 25 --> a= 2 , nothing about c ---> insuff
2. nothing about a --> insuff

1 and 2:
a=2 ---> 3^a = 9, we have c=36 ---> 4^b = 36/9= 4 --> b=1


Here`s where I get a little hazy....

If (3^a)*(4^b)=36, then doesn`t b have to equal 1?


if we know only c ..it's impossible to conclude that b=1 coz a and b are not necessarily integers :)


I still have a problem in agreeing with this reasoning. If a,b are not integers, how can lets say 3^1.25 * 4^3.45 equals an integer value?
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 [#permalink] New post 21 Jun 2006, 09:32
Guess I am way late to post for this.. but here goes

S1 :
5^a = 25 = 5^2
=> a = 2
=Don't know c
=> Not sufficient.

S2: c = 36
Don't know a; Not sufficient.

S1&S2:
a =2, c =36 => b = 1

Sufficient : Answer C
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 [#permalink] New post 22 Jun 2006, 06:42
sridhars wrote:

I still have a problem in agreeing with this reasoning. If a,b are not integers, how can lets say 3^1.25 * 4^3.45 equals an integer value?


How about my example?

Quote:
a could equal to (ln4/ln3+2) and b could equal to 0.

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 [#permalink] New post 22 Jun 2006, 06:53
the answer is B. There is no power of 3 that will yield 36
  [#permalink] 22 Jun 2006, 06:53
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