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

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Re: GMAT Prep 1: Symbolism [#permalink] New post 13 Feb 2010, 10:25
carriedinterest wrote:
For all positive integers m, M=3m when m is odd and M=1/2 when m is even. Which of the following is equivalent to 9 x 6?

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

Clear, concise explanations welcome!



It should be D.... Please check...

9 x 6 = (3x9) x (6 x 1/2) = 27 x 3 = 27
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Re: GMAT Prep 1: Symbolism [#permalink] New post 13 Feb 2010, 10:26
carriedinterest wrote:
LJ wrote:
You posted this question incorrectly because all of the answers need to be surrounded with a box, or in your notation, an underline. Failing to do this misses the point of the problem.


Good spot. I've corrected the answer choices. You're obviously familiar with the problem - care to answer?


9 = 27 and 6 = 3, multiplied together they = 81.

Because the answer choices are notated with the _, however, you need to calculate the "_" value of 81

When m is odd, 3m = 81, so m = 27
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GMAT Prep1: positive integer m [#permalink] New post 20 Feb 2010, 05:09
For all positive integers m, [m] = 3m when odd and [m] = (1/2)m when m is even. Which of the following is equal to [9]*[6]?

a) [81]
b) [54]
c) [36]
d) [27]
e) [18]

Last edited by pm4553 on 20 Feb 2010, 10:13, edited 1 time in total.
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Re: GMAT Prep1: positive integer m [#permalink] New post 20 Feb 2010, 07:04
[9]*[6]=(3 x 9)*(1/2 x 6) = (27) * (3) = 81

I think in the GMAT Prep question, there are square brackets around the answer also.

Only d, [27] = 3*27 = 81

Hence the answer.
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Re: GMAT Prep1: positive integer m [#permalink] New post 20 Feb 2010, 10:16
testprep2010 wrote:
[9]*[6]=(3 x 9)*(1/2 x 6) = (27) * (3) = 81

I think in the GMAT Prep question, there are square brackets around the answer also.

Only d, [27] = 3*27 = 81

Hence the answer.


Edited, thanks.

Even I picked A, unfortunately, it isn't correct. I have no clue WHY
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easy question and mysterios answer choice, pls help! [#permalink] New post 30 Apr 2010, 09:39
It is a question from GMATprep

question itself:
For all positive integers m, {m}=3m, when m is odd, and {m}=m/2 when m is even. which of the following is equivalent to {9}*{6} ?
a){81}
b){54}
c){36}
d){27}
e){18}

my solution:
solution seemed to me very easy 9 is odd and 6 is even so ={9*3}*{6/2}=27*3=81

and it is wrong! :?

pls help me.

p.s. OA I will put later.
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Re: Tough Algebra, Can anyone help me? Thanks!! [#permalink] New post 30 Apr 2010, 13:31
MSoS wrote:
Since the numbers are in boxes, we have to solve the Question twice.

First look at the given numbers (9 is odd so 3m, 6 is even so 1/2m)
[9]x[6] = 3(9)x1/2(6) = 81

Now look at 81 which is obviously odd which means that the answer has to be 3m = 81 (answer is also in a box)

hence, m = [27]



Thanks!
damn, I have to think twice, before doing such kind of questions.
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Re: GMAT Prep1: positive integer m [#permalink] New post 17 May 2010, 20:42
i made the same mistake with the boxes .....gmat is really smart with tricking you with such questions .....one thing that i noticed was that i make a lot of mistakes when converting the algebraic expression so lets say they asked about the product ...i will for some reason start adding in my calculation
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Re: GMAT Prep1: positive integer m [#permalink] New post 22 Jun 2010, 06:21
We need an eagle eye to crack this type.
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What means this: [m] (m in a square) ? [#permalink] New post 14 Nov 2010, 01:46
Hello,

I have some problems to solve this question:

For all positive integers m, [m] = 3m when m is odd and [m] = 0,5m when m is even. Which of the following is equivalent to [9] x [6] ?

A 81
B 54
C 36
D 27
E 18

_________________________________________________________________________

[m] is a m in a square

What do THEY want from me ??? m in a square, I've no idea what's the meaning of this sign.

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Re: What means this: [m] (m in a square) ? [#permalink] New post 14 Nov 2010, 02:18
Pepe wrote:
Hello,

I have some problems to solve this question:

For all positive integers m, [m] = 3m when m is odd and [m] = 0,5m when m is even. Which of the following is equivalent to [9] x [6] ?

A 81
B 54
C 36
D 27
E 18

_________________________________________________________________________

[m] is a m in a square

What do THEY want from me ??? m in a square, I've no idea what's the meaning of this sign.

Source: GMATPrep



[m] is being defined as a function, its the same thing as saying f(m) is a function such that ....

Now we need to find out [9] x [6]

[9] --> Since 9 is odd, [9]=3x9=27
[6] --> Since 6 is even, [6] = 0.5x6 = 3

Hence [9]x[6]=27x3=81
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Re: Very easy but still got wrong.. Need Your answer [#permalink] New post 14 Nov 2010, 09:11
Thank you guys.

I'll now focus always also on the answer choices, not only on the questions.

Didn't see, that the answers were also in squares.

:oops:
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Need help with these 5 GMAT Prep questions... [#permalink] New post 08 Dec 2010, 13:51
Guys,
as my G-day is approaching, I am putting more and more effort in improving my Quant. However, I seem to have troubles with some basic concepts. Below are the 5 questions which I know have simple explanations but are for some reason difficult for me to understand. If you can explain the solutions for any of them, I would greatly appreciate it! Cheers! :war

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Re: Tough Algebra, Can anyone help me? Thanks!! [#permalink] New post 26 Feb 2011, 23:18
IanStewart wrote:
We know that [9] = 3*9 = 27, since [x] = 3x when x is odd. We also know that [6] = 3, since [x] = x/2 when x is even. So [9]*[6] = 27*3 = 81.

Now, many people choose the wrong answer to this question, despite doing all of the work correctly, because they do not notice that the answer choices are all in boxes - a devious GMAT trap. So the answer choice which reads [81] is not equal to the number 81; it is equal to 3*81 = 243, because [x] = 3x when x is odd. The correct answer here is [27], which is equal to the number 81.


Thanks mate! This one was my big "AHA! Gotcha" GMAT moment for the day. A clever trap!
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Positive Integer m [#permalink] New post 29 Apr 2011, 01:03
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Re: Positive Integer m [#permalink] New post 29 Apr 2011, 01:55
I picked up 81 too :-(
Guess we have to first multiple 9*6=[54] then apply the rule of 1/2m = 1/2 * 54 = 27.

Question is why not 81?
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Re: Positive Integer m [#permalink] New post 29 Apr 2011, 05:54
You're ignoring the box symbol in the answer. Please try again bearing this in mind.
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Re: Positive Integer m [#permalink] New post 29 Apr 2011, 05:56
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[9] = 3*9 = 27

[6] = 3

So [9] * [6] = 81

but we need to pick one option among the answer choices with []

So [27] = 3*27 = 81

Answer - D
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Re: Positive Integer m [#permalink] New post 29 Apr 2011, 06:00
Excellent. Thank you subhashghosh.
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Re: Positive Integer m [#permalink] New post 29 Apr 2011, 06:52
Box 9 = 3*9 =27
Box 6 = 3

Box 9 * Box 6 = 27 *3 = 81

Calculating boxes in answer we can see that box 27 is the answer.

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Re: Positive Integer m   [#permalink] 29 Apr 2011, 06:52
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