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Help me with the logic for this - GMAT CD

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Help me with the logic for this - GMAT CD

by joefreddy » Sat Jan 12, 2008 10:38 pm
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?
Choice A 81
B 54
C 36
D 27
E 18

I choose 81 considering 9 and 6 seperately and then multiplying the result. The answer was 27 where first they multiplied 9 and 6 and then applied the above rule. Let me know why my logic was wrong ?
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by simplyjat » Sun Jan 13, 2008 2:13 am
The question is incomplete....

M = 3M, M = 2M do they make sense to you....
To know the correct answer write the correct question...

This makes me remember the good old question "The answer Answer to Life, the Universe, and Everything is 42"
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by joefreddy » Sun Jan 13, 2008 9:32 pm
Alright here is the screenshot of the question....
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by Stuart@KaplanGMAT » Sun Jan 13, 2008 9:37 pm
Where is that question from? Assuming that it's copied correctly, 81 should definitely be the right answer.

Basic order of operations dictates that we need to apply the box function to each individual integer and then mutiply the results together.

So:

9box = 3*9 = 27
6box = 1/2(6) = 3

27 * 3 = 81
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by simplyjat » Sun Jan 13, 2008 9:55 pm
Here you have to look at the answer choices, the answer choices do not mention the integer, but they mention integers with box operation applied.

so
9box * 6box = 3(9) * 6/2 = 81 the answer is 81 and not 81box...
now 27box = 3(27) = 81....

thus 9box * 3box = 27box.... And the original answer is correct....
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by Stuart@KaplanGMAT » Sun Jan 13, 2008 11:25 pm
Ahh, sorry - I didn't notice the boxes around the answers!
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