GRE Prep Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized
for You
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
What is the highest prime factor in the expression
[#permalink]
Updated on: 12 Dec 2017, 11:55
Updated on: 12 Dec 2017, 11:55
2
Bookmarks
00:00
Question Stats:
46% (01:00) correct
53% (01:04) wrong based on 13 sessions
Hide Show timer Statistics
What is the highest prime factor in the expression
\(\frac{3^{18} - 3^{12}}{3^5}\)
A) 3
B) 7
C) 11
D) 13
E) 19
\(\frac{3^{18} - 3^{12}}{3^5}\)
A) 3
B) 7
C) 11
D) 13
E) 19
Originally posted by shadowcatradz on 20 Feb 2017, 09:57.
Last edited by Carcass on 12 Dec 2017, 11:55, edited 3 times in total.
Last edited by Carcass on 12 Dec 2017, 11:55, edited 3 times in total.
Edited by Carcass
Re: What is the highest prime factor in the expression
[#permalink]
20 Feb 2017, 12:31
20 Feb 2017, 12:31
1
Expert Reply
Explanation
Take the expression
\(\frac{3^1^8 - 3^1^2}{3^5}\) or \(3^1^2\frac{3^6 - 1}{3^5}\)= \(3^7 \times 728\).
Clearly the highest prime factor of the expression \(\frac{3^1^8 - 3^1^2}{3^5}\) also is the highest prime factor of 728.
Try \(\frac{728}{19}\). Doesn't work!
Try \(\frac{728}{13}\). Works!
Hence D is the right answer.
Take the expression
\(\frac{3^1^8 - 3^1^2}{3^5}\) or \(3^1^2\frac{3^6 - 1}{3^5}\)= \(3^7 \times 728\).
Clearly the highest prime factor of the expression \(\frac{3^1^8 - 3^1^2}{3^5}\) also is the highest prime factor of 728.
Try \(\frac{728}{19}\). Doesn't work!
Try \(\frac{728}{13}\). Works!
Hence D is the right answer.
gmatclubot
Re: What is the highest prime factor in the expression [#permalink]
20 Feb 2017, 12:31
Moderators:
