June 2007 - Sec 1 - Game 1 - Q2

Moving to Question 2, Which one of the following must be true about any acceptable

product code?

Let's take a look here at (A), digit 1 appears in some position before digit 2.

Well, looking at our previous work from Question 1, we see digit 1 after digit 2 so (A) does

not follow, doesn't have to be true, so (A) would be out. Again, coming from Question

1.

(B), the first digit appears in some position before the third digit. Again, coming directly

from our previous work in Question 1, we see the third digit appear before the first digit

or the first digit appear after the third digit, so again B doesn't have to be true

coming directly from Question 1.

(C), the second digit appears in some position before the third digit. And if you notice

in our 2 scenarios, in scenario 1 digit 2 is second and 3 would come somewhere in 3,

4 or 5, which clearly means that 2 appears before 3. In scenario 2, 2 is first so clearly

3 must appear after 2.

So you notice in both of our scenarios, 2 appears before 3 so (C) must be true and (C)

would be the correct answer.