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For all positive integers m, [m]=3m when m is odd and [m]=

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For all positive integers m, [m]=3m when m is odd and [m]= [#permalink] New post 10 Nov 2005, 04:57
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Question Stats:

52% (01:27) correct 48% (00:24) wrong based on 81 sessions
For all positive integers m, [m]=3m when m is odd and [m]=(1/2)m when m is even. Which of the following is equivalent to [9] * [6]?

A) [81]
B) [54]
C) [36]
D) [27]
E) [18]

OPEN DISCUSSION OF THIS QUESTION IS HERE: for-all-positive-integers-m-3m-when-m-is-odd-125937.html?hilit=equivalent
[Reveal] Spoiler: OA

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 [#permalink] New post 10 Nov 2005, 05:16
D
9=3*9
6=1/2*6

9*6= 3*9*3=81

Take D 27=3*27=81
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 [#permalink] New post 10 Nov 2005, 05:51
For all positive integers m, m = 3m when m is odd and m = (1/2)m when m is even. Which of the following is equivalent to 9 x 6 ?

(A)

9 is odd so 9*3=27.
6 is even so 6/2=3.
27*3=81

Surely I must be overlooking something...
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 [#permalink] New post 10 Nov 2005, 12:27
up 81 =27* 3

so 27 is the answer.

so D it is.
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 [#permalink] New post 10 Nov 2005, 13:05
OA is D

Thanks guys, was a little confused about this one.
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explanations [#permalink] New post 10 Nov 2005, 17:13
:? Pretty confusing exercise!!! I would have say A as well
seems there is a trap here can anyone explain why it is 27

Thanks
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Re: explanations [#permalink] New post 10 Nov 2005, 17:36
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mand-y wrote:
:? Pretty confusing exercise!!! I would have say A as well
seems there is a trap here can anyone explain why it is 27

Thanks


Remember the answer also has underline so you have to tailor the answer to that

81 = 3 * 27 (odd)

hence 27
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GMAT Prep - confusing question [#permalink] New post 19 Oct 2006, 20:15
For all positive integers M, [M] = 3M when M is odd and [M] = 1/2M when M is even. Which of the following is equivalent to [9] * [6]?

Choices: A) 81 B) 54 C) 36 D) 27 E) 18

How is the answer not 81?
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 [#permalink] New post 19 Oct 2006, 20:34
it is possible only when [M] = 1/2 * M = M / 2 when M is even
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 [#permalink] New post 19 Oct 2006, 20:51
right, I agree...it is given in the instructions...[M] = M/2 when M is even...i guess I am confused about the order of operations...if you do the dictated operations FIRST then you get 81...if you multiply 9 times 6 First then you get 54 which is even and then taking half you get 27 which is apparently the right answer. I think it is poorly worded or a mistake. There is nothing to indicate that you need to do the multiplication first.

I guess there are a lot of questions like this...where you get some kind of rule imposed on numbers, and i always thought that takes precedence over regular operations.
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Re: GMAT Prep - confusing question [#permalink] New post 19 Oct 2006, 21:07
primeminister wrote:
For all positive integers M, [M] = 3M when M is odd and [M] = 1/2M when M is even. Which of the following is equivalent to [9] * [6]?

Choices: A) 81 B) 54 C) 36 D) 27 E) 18

How is the answer not 81?

[9]M is odd so [M] = 3M-->9*3=27
[6]M is even so [M] = 1/2M-->6/2=3
27*3=81
Hope this helps
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 [#permalink] New post 19 Oct 2006, 21:22
Yurik I fully agree with you. The official answer according to GMATprep is 27. That is why i was confused. Thanks
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 [#permalink] New post 20 Oct 2006, 05:24
primeminister wrote:
Yurik I fully agree with you. The official answer according to GMATprep is 27. That is why i was confused. Thanks


exactly.. I got this question wrong too because of incorrect order of operations..

would someone explain?
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Re: GMAT Prep - confusing question [#permalink] New post 20 Oct 2006, 07:58
primeminister wrote:
For all positive integers M, [M] = 3M when M is odd and [M] = 1/2M when M is even. Which of the following is equivalent to [9] * [6]?

Choices: A) 81 B) 54 C) 36 D) 27 E) 18

How is the answer not 81?



There is somthing wrong with this question unless I missing something.

1) Say you do what the problem asks:
[9]=3(9)
= 27

AND

[6]=1/2(6)
=3

3 x 27 = 81


2) Now say you misread the question and confused the formulas for even and odd you still get the same answer:

[6]=3(6)
=18

AND

[9]=1/2(9)
=4.5

4.5 x 18 = 81


Ideas anyone?
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 [#permalink] New post 20 Oct 2006, 09:50
For all positive integers M, [M] = 3M when M is odd and [M] = 1/2M when M is even. Which of the following is equivalent to [9] * [6]?

Choices: A) 81 B) 54 C) 36 D) 27 E) 18


[9]*[6] = 27* 3 = 81

[X] = 81 SO X = 81/3 ( BECAUSE X HAS TO BE INTIGER AND 81 IS NOT DEVISIBLE BY TWO)

THUS

X = 27 AND [27] = 3*27 = 81

mY ANSWER IS D
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Re: GMAT Prep - confusing question [#permalink] New post 20 Oct 2006, 10:14
primeminister wrote:
For all positive integers M, [M] = 3M when M is odd and [M] = 1/2M when M is even. Which of the following is equivalent to [9] * [6]?

Choices: A) 81 B) 54 C) 36 D) 27 E) 18

How is the answer not 81?


Shouldn't the answer be D only when choice D is [27] and not 27? Is there a mistake in the answer choices? should the choices be: A) [81] B) [54] C) [36] D) [27] E) [18]
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 [#permalink] New post 21 Oct 2006, 09:54
yezz wrote:
For all positive integers M, [M] = 3M when M is odd and [M] = 1/2M when M is even. Which of the following is equivalent to [9] * [6]?

Choices: A) 81 B) 54 C) 36 D) 27 E) 18


[9]*[6] = 27* 3 = 81

[X] = 81 SO X = 81/3 ( BECAUSE X HAS TO BE INTIGER AND 81 IS NOT DEVISIBLE BY TWO)

THUS

X = 27 AND [27] = 3*27 = 81

mY ANSWER IS D

yezz did you meen A?
81 is A and D is 27 :wink:
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 [#permalink] New post 21 Oct 2006, 10:14
I just did this question on a GMAT prep test, and the answer choices are in brackets, indicating that the answers themselves are subject to the function listed in the question (the function is also in brackets). So since the answer is 81, and 81 is odd, then it's answer D, because [27] means you multiply 27 by 3, which is 81.
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 [#permalink] New post 21 Oct 2006, 10:19
guys, the question is not asking for the result of [9] * [6], but its equivalent (which of the following answers, when multiplied by 3 or divided by 2, equals 81 too). I hope this helps.

Choices: A) 81 B) 54 C) 36 D) 27 E) 18


[9]*[6] = 27* 3 = 81

[X] = 81 SO X = 81/3 ( BECAUSE X HAS TO BE INTIGER AND 81 IS NOT DEVISIBLE BY TWO)

THUS

X = 27 AND [27] = 3*27 = 81 from yess
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GMAT Prep, question 3 [#permalink] New post 28 Sep 2009, 21:04
Hi, I couldn't figure this out on the GMAT Prep. It's question number 3:

For all positive integers m, [m] = 3m when m is odd and [m] = (1/2)(m) when m is even. Which of the following is equivalent to [9] x [6]?

A. 81

B. 54

C. 36

D. 27

E. 18

I already know what the correct answer is so I just want to know the math that derives the correct answer. Any help would be appreciated. Thanks!
GMAT Prep, question 3   [#permalink] 28 Sep 2009, 21:04
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