Thursdays With Ron: Prime Boxes

by Manhattan Prep, Jun 17, 2010

This is the third installment of our Thursdays with Ron posts. Every other Thursday, our instructor Ron Purewal (known on the Beat the GMAT forums as lunarpower) hosts a free study hall session, where anyone can submit questions ahead of time and attend. Ron chooses a few themes from the questions he gets and goes over strategies for them.

In this recording, Ron goes over Prime Boxes:

Heres an outline of what Ron covers, with the minute markers parenthesis. Make sure to watch the video, though, so that youre able to follow along!

• Rons warning: (0:00) These questions (primes and divisibility) tend to be difficult for many people.
• What is a Prime Box? (1:15) Its the Manhattan GMAT tool for depicting the content of a numbers prime factorization.
• Three questions you should be thinking about when you consider the impact of a statement on a numbers prime box: (6:10) 1. What numbers, if any, must be in the prime box? 2. What numbers, if any, may or may not, be in the prime box? What numbers, if any, cannot be in the prime box?
• Example: (7:50) Ron puts up a divisibility example (n is divisible by 12 AND n is divisible by 20) and before he begins to consider the three questions, he describes how to combine the two statements in his example.
• What numbers may or may not be in the prime box? (12:47) Ron answers this question for the example above.
• What numbers, if any, cannot be in the prime box? (14:42) Ron answers this question for the example above.
• Another example: (15:20) n is NOT divisible by 12 is discussed.
• What numbers, if any, MUST be in the prime box? (16:00)
• Ron answers questions 2 and 3 together: (18:09) He does this, because, he notes, you cant answer them separately.

If you want to view recordings of past Thursdays with Ron or submit questions for the next live session, which takes place on June 24, you can do so here.