prime number issues

Expert replies

francoisph: Master | Next Rank: 500 Posts; Posts: 124; Joined: Sun Mar 07, 2010 3:15 pm; Thanked: 1 times

by francoisph » Tue May 04, 2010 4:35 am

hi

please do you have a technique to memorize the prime numbers ?

ex:
what are the first five prime numbers greater than 50?

Like this post

Source: Beat The GMAT — Problem Solving | Tue May 04, 2010 4:35 am

pradeepkaushal9518: Legendary Member; Posts: 1309; Joined: Wed Mar 17, 2010 11:41 pmFollowed by: 5 members; Thanked: 33 times

by pradeepkaushal9518 » Tue May 04, 2010 7:03 am

51,53,57,59,61

as they are divisible by them only. no need to memorise

Like this post

kstv: Legendary Member; Posts: 610; Joined: Fri Jan 15, 2010 12:33 amFollowed by: 2 members; Thanked: 47 times

by kstv » Tue May 04, 2010 8:35 am

51 & 57 are divisible by 3.
use the strings "prime numbers 1-100" in Google.
Ans to ur Q 53 59 61 67 71

Like this post

pradeepkaushal9518: Legendary Member; Posts: 1309; Joined: Wed Mar 17, 2010 11:41 pmFollowed by: 5 members; Thanked: 33 times

by pradeepkaushal9518 » Tue May 04, 2010 8:42 am

sorry i hvt checked 51 n 57

Like this post

tpr-becky: GMAT Instructor; Posts: 509; Joined: Wed Apr 21, 2010 1:08 pmFollowed by: 85 members; Location: Irvine, CA; Thanked: 199 times; GMAT Score:750

by tpr-becky » Tue May 04, 2010 9:46 am

Why would you want to memorize them? sounds like a lot of effort for a little reward - it is better to know the rules of divisibility for the numbers from 2-11 and check divisibility if you are looking for primes - less room for error and almost as fast if you get good at divisibility rules which will help you on every area of the test.

Becky
Master GMAT Instructor
The Princeton Review
Irvine, CA

Like this post

francoisph: Master | Next Rank: 500 Posts; Posts: 124; Joined: Sun Mar 07, 2010 3:15 pm; Thanked: 1 times

by francoisph » Tue May 04, 2010 1:32 pm

because you have 2 minutes to find the result

wasted time I think if you should count on various numbers (div by itself and 1 )

Like this post

kstv: Legendary Member; Posts: 610; Joined: Fri Jan 15, 2010 12:33 amFollowed by: 2 members; Thanked: 47 times

by kstv » Tue May 04, 2010 4:38 pm

@ francoisph
Is it possible to post the particular Q where you had to use the knowledge of prime nos. ? Thnaks.

Like this post

maheshban: Newbie | Next Rank: 10 Posts; Posts: 3; Joined: Fri Mar 19, 2010 11:22 pm

by maheshban » Tue May 04, 2010 11:25 pm

This might help

1.write down all the odd nos from the no given (In ur example 50)

I,e 51,53,55,57,59,61,6365,67,69,71

2.cancle the nos that are divisible,ex:51--sum is 6 ,so div by 3 ,cancle it ,lly u can eliminate the remaining

so 53,59,61, 67 ,71..

(u should know the divisibility rules though)

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

559 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 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