Properties of number

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sam0575: Newbie | Next Rank: 10 Posts; Posts: 4; Joined: Fri May 09, 2014 1:41 am

Properties of number

by sam0575 » Tue May 13, 2014 2:00 am

Hello

When it comes to problem solving in GMAT I do quiet well except when I'm given properties of numbers questions such as "whats is the greatest integer k for which 3^k is a factor of p/which of the following is not a factor of n....."

I think I lack knowledge in this area and don't know how to make progress...

Any suggestion ?

Thank you very much !

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Source: Beat The GMAT — Problem Solving | Tue May 13, 2014 2:00 am

Matt@VeritasPrep: GMAT Instructor; Posts: 2630; Joined: Wed Sep 12, 2012 3:32 pm; Location: East Bay all the way; Thanked: 625 times; Followed by:119 members; GMAT Score:780

by Matt@VeritasPrep » Tue May 13, 2014 12:35 pm

Practice, practice, practice! Most people haven't encountered this sort of math in school (or anywhere else) before, so there's a lot to learn.

There are lots of good GMAT books on the topic - our Veritas Arithmetic book, for instance - but the real key is finding questions to practice and review. There are plenty of summaries out there too, but IMHO it's much better to learn from problems: we have some good ones here.

Another resource I love, though it may be more comprehensive than a GMAT student needs, is Art of Problem Solving's Number Theory book. It isn't a GMAT book (it's designed to train kids for national and international math competitions) but it's a genuine introduction and if you make your way through it you'll be fluent in the subject.

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by [email protected] » Tue May 13, 2014 12:47 pm

Hi sam0575,

Number Properties are the patterns/rules behind how math "works"; you can spot them by the math "vocabulary words" that are used to describe a given variable (re: odd, even, positive, negative, factor, prime, etc.). All of these questions can be solved by TESTing VALUES; this approach tends to work really well since it takes what seems like a broad concept and grounds it in a real-word example.

For instance, if a question tells you that A, B and C are all ODD INTEGERS and asks about A+B+C, then you can either use what you know about adding up odd integers (the Number Property) or you can TEST VALUES.

Number Property:
Odd + Odd = Even
Even + Odd = Odd

So, Odd + Odd + Odd = Odd

TEST VALUES:
Choose 3 ODD INTEGERS: 1, 3 and 5
1 + 3 + 5 = 9

So, adding up 3 ODD INTEGERS gives us an ODD INTEGER.

Obviously, getting in plenty of reps should help you to improve, but there's another facet to studying that most Test Takers tend to ignore....Just because you got a question right doesn't mean that your approach was the only approach. Revisiting old questions and attempting to solve them in different ways can really help to improve your overall skill set.

GMAT assassins aren't born, they're made,
Rich

Contact Rich at [email protected]