Bunuel wrote:

What is the value of integer z?

(1) z is the remainder when positive integer x is divided by positive integer (x – 1)

(2) x is not a prime number

Kudos for a correct solution.

VERITAS PREP OFFICIAL SOLUTION:Now look at statement 1. There’s a lot to unpack – the concept of remainder, the definitions of “positive integer x and positive integer (x – 1)”, the fact that x then can’t be 1 (or x-1 would be 0 and therefore prohibited), the fact that the two values being divided are consecutive integers. So it’s not surprising that, on their way to the trap answer selected by nearly 60% of respondents in the

Veritas Prep Question Bank, many feel the glory when they unravel the variables and processes and think:

“Ah, ok. 5/4 would work and that’s 1 remainder 1. 10/9 would work and that’s 1 remainder 1. 100 divided by 99 would work and that’s 1 remainder 1. I get it…remainder is always 1.”

After all that work, statement 2 is as much a formality as a 2 run lead with no baserunners in the 9th inning. Piece of cake. So people start to hear that crowd chanting their name a-la “De-rek-Jeeeet-er”, they pat themselves on the back for the accomplishment, and they pick A. Without ever seeing the opportunity that statement 2 really should provide them:

“Wait…that’s not the script I want – it shouldn’t be that easy.”

Those who know the GMAT well – those Jeterian scholars who have honed their craft through practice and determination to go with the natural talent – look at statement 2 and think “why does this matter? Why would the author write such a mundanely-irrelevant statement? The question is about z and the statement is about x? Come on…”

And in doing so, they’ll ask “Why would a prime number matter? And what kind of prime numbers might change things?” And when you’re talking prime numbers, just like when you’re talking Yankee lore, you have to bring up Number 2. 2 is the only even prime number and it’s the lowest prime number. If you see the definition “prime” and you don’t consider 2, you’re probably making a mistake. So statement 2 here should be your clue to test x = 2 and realize:

2/1 = 2 with no remainder. Based on statement 1 alone the answer is almost always “remainder 1″ but this one exception allows for a remainder of 0, proving that statement 1 is not sufficient. You need statement 2 to rule it out, making

the answer C (for captain?).

The real takeaway here?

Even if you think you’ve “won” after statement 1, if statement 2 looks so much like a mere formality that it’s almost anti-climactic there’s a good chance it’s there as a clue. Ask yourself why statement 2 might matter – sometimes it will and sometimes it won’t, but it’s always worth checking in these cases – and you may find that the real “glory” you’re after requires you to take a step back from that “win” you thought you had earlier on.

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