## GMAT Tip of the Week: Prime Cut

*Posted on on November 11, 2011*

In case you missed it, today’s date is a rather fun one: 11/11/11. (It’s also a date that Europeans and Americans write the same way. No fretting over “Should the day or month come first?” here.) Next year we’ll have a 12/12/12, but then after that the “fun” dates will be few and far between. While we still have this fun date to enjoy — three prime numbers in a row! — let’s revisit a lesson from the past about how to quickly break down larger numbers and determine whether or not they’re prime.

Let’s look at 2011. Is it a prime number? You could spend at least a few minutes trying to answer this question if you’re not careful. But if you think strategically, it needn’t take that long, and you can likely complete your “prime test” even within the two-minutes-per-question time allotment that the GMAT would give you for a question that, as so many do, requires your knowledge of prime numbers and divisibility. Here’s how to get started: