Prime Factor

Expert replies

Previous Topic Next Topic

candygal79: Senior | Next Rank: 100 Posts; Posts: 49; Joined: Mon Feb 10, 2014 1:18 amFollowed by: 3 members

by candygal79 » Fri Apr 04, 2014 12:22 am

What is the sum of different positive Prime Factor of 550 ?

A 10

B 11

C 15

D 16

E 18

Like this post

Source: Beat The GMAT — Problem Solving | Fri Apr 04, 2014 12:22 am

GMAT/MBA Expert

Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

by Brent@GMATPrepNow » Fri Apr 04, 2014 12:30 am

candygal79 wrote:What is the sum of different positive Prime Factor of 550 ?

A 10

B 11

C 15

D 16

E 18

550 = (2)(5)(5)(11)
So, the DIFFERENT prime factors are 2, 5 and 11
2 + 5 + 11 = [spoiler]18 = E[/spoiler]

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

Like this post

GMAT/MBA Expert

[email protected]: Elite Legendary Member; Posts: 10392; Joined: Sun Jun 23, 2013 6:38 pmFollowed by: 511 members; Location: Palo Alto, CA; Thanked: 2867 times; GMAT Score:800

by [email protected] » Fri Apr 04, 2014 1:29 pm

Hi candygal79,

There's a math rule called 'prime factorization' that you might occasionally use on the GMAT. The idea is that any positive number can be "broken down" into a bunch of prime numbers that are multiplied together (unless the number is already prime).

eg 10 = 2x5

Here, we're asked to prime factor 550; this can be done in a set of steps.

550 = 55x10

55 = 5x11
10 = 2x5

So 550 = 2x5x5x11

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

Contact Rich at [email protected]

Like this post

Abhishek009: Master | Next Rank: 500 Posts; Posts: 359; Joined: Wed Mar 11, 2009 4:37 amFollowed by: 2 members; Location: Kolkata, India; Thanked: 50 times

by Abhishek009 » Sat Apr 05, 2014 7:12 am

candygal79 wrote:What is the sum of different positive Prime Factor of 550 ?

A 10

B 11

C 15

D 16

E 18

Find the factors of 550

550 = 5^2 X 2 X 11

Now we are required to find only the sum of different positive Prime Factor of the number , so the sum is -

5 + 2 + 11 => 18

Abhishek

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