Maths problem

Expert replies

Previous Topic Next Topic

way2ashish: Senior | Next Rank: 100 Posts; Posts: 32; Joined: Mon Sep 26, 2011 6:34 pm

by way2ashish » Sat Dec 29, 2012 2:13 am

Q) What is the greatest prime factor of 4^5 - 16?
1

2

3

5

Like this post

Source: Beat The GMAT — Problem Solving | Sat Dec 29, 2012 2:13 am

GMAT/MBA Expert

Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pmFollowed by: 523 members; Location: Milpitas, CA; Thanked: 1854 times; GMAT Score:770

by Anurag@Gurome » Sat Dec 29, 2012 4:42 am

way2ashish wrote:Q) What is the greatest prime factor of 4^5 - 16?

(4^5 - 16) = (4^5 - 4^2) = (4^2)*(4^3 - 1) = (2^4)*(64 - 1) = (2^4)*63 = (2^4)*7*9 = (2^4)*(3^2)*7

Hence, the greatest prime factor of (4^5 - 16) is 7

Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/

Like this post

ritind: Senior | Next Rank: 100 Posts; Posts: 47; Joined: Wed Nov 21, 2012 10:40 pm; Thanked: 4 times

by ritind » Sun Dec 30, 2012 4:00 am

Anurag sir there's no 7 in the option
So the ans shld be 3

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