Prime Factorization: My single favorite topic on the GMAT. It’s not even a contest.

My passionate (some would say evangelical!) advocacy of prime factorization results not only from my finding prime numbers so inherently fascinating in and of themselves, but also from the plain and simple truth that prime factorization proves surprisingly useful on questions on which prime numbers aren’t even mentioned.

For example, any time you’re given a question asking about multiples and factors, you can bet that prime factorization will help you get to the answer quicker.

Case in point — this Data Sufficiency question from the Official GMAT Guide:

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Data Sufficiency questions are often difficult to get used to, because they require an adjustment in your approach to math problems. When you went through math classes growing up, the end goal was always “Find the value of x” or “Find the area of this circle.” You were asked to give hard responses to these questions, and nothing mattered more than finding a definite value.

With Data Sufficiency, answering the question does not matter as much as the ability to answer the question. You are not primarily concerned with the final answer, but rather whether you have enough information to get you to that answer. For example, if you’re asked to find the value of x, and a statement tells you that 300x + 257 = 1345, you know that this statement is sufficient, because you can perform arithmetic on that equation to isolate x. Are you going to perform it? No, because it’s too complicated and you don’t need to! All you’re concerned with is whether you can find the answer.

Our friends at GMAT Club released a handy iPhone app a few months ago.  If you’re on the go, you can still get extra Quantitative questions, time your practice tests, and learn from their detailed user forums. Last week it was in the App Store’s “What’s Hot” List, so it’s a great time to get [...]

David Kuntz developed the algorithm for Knewton’s GMAT prep course, and this is the final installment in his CAT FAQ. For more info, check out part 1 and part 2.
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How can my overall percentile be higher than both my quantitative and verbal percentiles?
Your overall score is calculated separately from your section scores, so you can [...]

David Kuntz is Vice President, Research at Knewton, where he builds the CATs for its online GMAT course. This is part 2 in a series of posts about the algorithm behind the GMAT.
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How is the GMAT actually scored? Here are some more questions that students frequently have about its algorithm.
1. My score doesn’t seem to [...]

Rich Zwelling is one of the expert teachers in Knewton’s GMAT course. “Combinatorics” is  a word he throws around casually.
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I was recently discussing a particular GMAT problem with a friend, and as so often happens with standardized-test nerds, the discussion turned into an extended analysis.  We can’t help ourselves, I suppose.
The question went something like [...]

Rich is one of the stellar teachers in Knewton’s GMAT course, in whch he loves helping students rock the Quantitative section.
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In any GMAT prep course, one of the first things taught about the Data Sufficiency section is that the two statements are true and do not contradict one another.  It’s a point that’s easy to [...]

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David Kuntz is Vice President, Research at Knewton, where he builds the CATs for its online GMAT course.
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I’ve received a number of inquiries from the community about the GMAT algorithm, so I thought it best to reply in article form. Here are some frequently asked questions about computer-adaptive tests (CATs).
1. What’s an algorithm?
An algorithm, generally, [...]