GMATPrep - Another trap - The Beat The GMAT Forum - Expert GMAT Help & MBA Admissions Advice

GMATPrep - Another trap

Expert replies

givemeanid: Master | Next Rank: 500 Posts; Posts: 277; Joined: Sun Jun 17, 2007 2:51 pmFollowed by: 1 member; Location: New York, NY; Thanked: 6 times

by givemeanid » Mon Sep 03, 2007 9:09 am

I came across this while taking a GMATPrep test.

If k is a positive integer, then 20k is divisible by how many different positive integers?

1. k is prime
2. k = 7

So It Goes

Like this post

Source: Beat The GMAT — Data Sufficiency | Mon Sep 03, 2007 9:09 am

agps: Master | Next Rank: 500 Posts; Posts: 101; Joined: Tue Aug 07, 2007 1:45 amFollowed by: 1 member

by agps » Mon Sep 03, 2007 9:22 am

I would answer D (either)

2) (easier) 20k = 20*7 = you know the number then you can determine all possible factors, sufficient.

1) any prime is divisible only by itself and 1. any prime multiplied by 20 will be divisible by it's factors and the factors of 20 (2, 4, 5, 10) so it's sufficient.

OA?

Like this post

givemeanid: Master | Next Rank: 500 Posts; Posts: 277; Joined: Sun Jun 17, 2007 2:51 pmFollowed by: 1 member; Location: New York, NY; Thanked: 6 times

by givemeanid » Mon Sep 03, 2007 9:37 am

That's why its a trap son

Try it again. D is not the OA

So It Goes

Like this post

agps: Master | Next Rank: 500 Posts; Posts: 101; Joined: Tue Aug 07, 2007 1:45 amFollowed by: 1 member

by agps » Mon Sep 03, 2007 9:48 am

hmmm,
is it because of 2? 2 is a prime, but also a factor of 20, then, not knowing what prime nuber it is you can't be sure if you have 4 different factors (for 2) or 5 (for any other prime number)

it that case, the answer would be B.

Like this post

givemeanid: Master | Next Rank: 500 Posts; Posts: 277; Joined: Sun Jun 17, 2007 2:51 pmFollowed by: 1 member; Location: New York, NY; Thanked: 6 times

by givemeanid » Mon Sep 03, 2007 12:47 pm

Now you got it. You have to consider 2 (or 5) as a value of k!

So It Goes

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

563 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (563 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review