positive integer m

[m] = 3m for all odd m; [m] = 1/2m for all even m. solve [9] X [6]?

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

It is true that [9] x [6] = 81.
9 is odd, so [9] = (3)(9) = 27
6 is even, so [6] = 6/2 = 3
So, [9] x [6] = 27 x 3 = 81

However, the answer choices are as follows:
a) [81]
b) [54]
c) [37]
d) [27]
e) [18]

So, which of these 5 answer choices equals 81?

Since 27 is odd, [27] = (3)(27) = 81

So, the correct answer is D

Cheers,
Brent

Hi anant03,

Brent has correctly explained the math behind this question, so I won't rehash that material here.

This is an example of a "symbolism" question, in which the prompt "makes up" a math symbol, tells you what it means, and asks you to perform a basic calculation with it. You'll likely see 1 of these on the Official GMAT and you appeared to handle the bulk of the work just fine.

You ARE expected to use the symbol wherever it appears, so realizing the symbol appears in the answer choices means that you had a bit more work to do. This "twist" on a symbolism question isn't too common, but as you do better and better in the Quant section, the GMAT will adapt to you and give you more questions that require slightly more work (or that have "twists"). Be on the lookout for those details as you continue to study.

GMAT assassins aren't born, they're made,
Rich

IF the answer choices were
a) 81
b) 54
c) 37
d) 27
e) 18
Then we'd just select A.

But, the answer choices aren't given as regular numbers. They're given as boxed numbers that require us to find their value (using the given formula).

Cheers,
Brent