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Moving to question one: If the last digit
of an acceptable product code is 1, it must

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Alright so let's draw out a hypothetical for
question one here. What it says is that the

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last digit of an acceptable product code is
1. Well if the last digit is 1, we know for

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certain that we are going to be in scenario
two because 1 in scenario one is appearing

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So since we're in scenario two we know that 2 is going to be first; 4 is going to be second

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because it's exactly twice the first value,
or the first digit. Now what do we have left?

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We have 0 and 3. We know that the third digit must less than the fifth digit, which means

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0 must third, leaving 3 for four. So which
one of the following must be true

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(A), the first digit is 2. And you notice
that must be true so (A) would be the correct

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But again just going through the rest of these really quickly just to show you . . .

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(B), the second digit is 0. No, in this
case it is 4 and if it must be true it's always

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the case. So one counter example would eliminate B.

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(C), the third digit is 3. Again, the
only possibility is that the third digit is

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(D), the fourth digit is 4. Again, the
fourth digit is 3 so D does not follow.

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(E), the fourth digit is 0. Again, we
know that the fourth digit is 3. So (A) would

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be the correct answer.