For all positive integers \(m, [m] = 3m\) when \(m\) is odd and \([m] = \dfrac{m}2\) when \(m\) is even. What is

[Vincen]

For all positive integers \(m, [m] = 3m\) when \(m\) is odd and \([m] = \dfrac{m}2\) when \(m\) is even. What is \([9]\cdot [6]\) equivalent to?

A. \([81]\)

B. \([54]\)

C. \([37]\)

D. \([27]\)

E. \([18]\)

Answer: D

Source: GMAT Prep

[Brent@GMATPrepNow]

For all positive integers \(m, [m] = 3m\) when \(m\) is odd and \([m] = \dfrac{m}2\) when \(m\) is even. What is \([9]\cdot [6]\) equivalent to?

A. \([81]\)

B. \([54]\)

C. \([37]\)

D. \([27]\)

E. \([18]\)

Answer: D

Source: GMAT Prep

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

BEFORE you select answer choice A, notice that 81 has brackets around it.
Since 81 is odd, [81] = (3)(81) = 243
So, answer choice A is NOT correct.

So, which of the 5 answer choices equals 81?

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

So, the correct answer is D

Cheers,
Brent