June 2007 - Sec 1 - Game 1 - Q2

Video Transcript:

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Moving to Question 2, Which one of the following must be true about any acceptable
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product code?
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Let's take a look here at (A), digit 1 appears in some position before digit 2.
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Well, looking at our previous work from Question 1, we see digit 1 after digit 2 so (A) does
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not follow, doesn't have to be true, so (A) would be out. Again, coming from Question
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1.
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(B), the first digit appears in some position before the third digit. Again, coming directly
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from our previous work in Question 1, we see the third digit appear before the first digit
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or the first digit appear after the third digit, so again B doesn't have to be true
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coming directly from Question 1.
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(C), the second digit appears in some position before the third digit. And if you notice
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in our 2 scenarios, in scenario 1 digit 2 is second and 3 would come somewhere in 3,
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4 or 5, which clearly means that 2 appears before 3. In scenario 2, 2 is first so clearly
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3 must appear after 2.
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So you notice in both of our scenarios, 2 appears before 3 so (C) must be true and (C)
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would be the correct answer.