Moving to question one: If the last digit
of an acceptable product code is 1, it must
Alright so let's draw out a hypothetical for
question one here. What it says is that the
last digit of an acceptable product code is
1. Well if the last digit is 1, we know for
certain that we are going to be in scenario
two because 1 in scenario one is appearing
So since we're in scenario two we know that 2 is going to be first; 4 is going to be second
because it's exactly twice the first value,
or the first digit. Now what do we have left?
We have 0 and 3. We know that the third digit must less than the fifth digit, which means
0 must third, leaving 3 for four. So which
one of the following must be true
(A), the first digit is 2. And you notice
that must be true so (A) would be the correct
But again just going through the rest of these really quickly just to show you . . .
(B), the second digit is 0. No, in this
case it is 4 and if it must be true it's always
the case. So one counter example would eliminate B.
(C), the third digit is 3. Again, the
only possibility is that the third digit is
(D), the fourth digit is 4. Again, the
fourth digit is 3 so D does not follow.
(E), the fourth digit is 0. Again, we
know that the fourth digit is 3. So (A) would
be the correct answer.