substitution practice Q

[wvspidermonkey]

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

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

My answer: 3m * 1/2(m) OR 3(9)*(1/2)(6) = 27*3 = 81 or A.

Formal Answer: D.

What did I miss?

Thank you! A

[kevin]

The answers are also in boxes!

[wvspidermonkey]

I'll be danged... is there a way that I can catch this type of trick? I didn't think of the twist... 3m=81 =>81/3 => m=27. Is there a better or faster way to catch twists like this?

Thank you!
A

[lerckin]

I'll be danged... is there a way that I can catch this type of trick? I didn't think of the twist... 3m=81 =>81/3 => m=27. Is there a better or faster way to catch twists like this?

Thank you!
A

why 3m=81 and why 81/3 ?

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

9(in box)* 6 (in box) =27*3=81

[KK09]

Step 1 > 9x6 = 54 "i.e M =54"
step 2 > determine if even or odd ...its even
STEP3 > 1/2M = 54 * 1/2 = 27

OPTION D

THE QUESTIONS SPEAKS ABOUT IF THE EVENT WILL BE ODD OR EVEN..