Last visit was: 22 Nov 2024, 16:45 It is currently 22 Nov 2024, 16:45

Close

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

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GRE score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel
Verbal Expert
Joined: 18 Apr 2015
Posts: 30003
Own Kudos [?]: 36355 [0]
Given Kudos: 25927
Send PM
avatar
Intern
Intern
Joined: 17 Feb 2020
Posts: 16
Own Kudos [?]: 67 [0]
Given Kudos: 0
Send PM
avatar
Manager
Manager
Joined: 22 Aug 2019
Posts: 96
Own Kudos [?]: 85 [0]
Given Kudos: 0
Send PM
User avatar
GRE Instructor
Joined: 19 Jan 2020
Status:Entrepreneur | GMAT, GRE, CAT, SAT, ACT coach & mentor | Founder @CUBIX | Edu-consulting | Content creator
Posts: 117
Own Kudos [?]: 265 [0]
Given Kudos: 0
GPA: 3.72
Send PM
Re: If p is a positive integer, which of the following could be [#permalink]
Carcass wrote:
If p is a positive integer, which of the following could be a prime number?

(A) 8p

(B) 8p + 1

(C) 8p + 2

(D) 8p + 4

(E) 8p + 6


Kudos for the right answer and explanation



All of the options (A, C, D, and E) are multiple of 2:

8p = 2 * 4p
8p + 2 = 2 * (4p + 1)
8p + 4 = 2 * (4p + 2)
8p + 6 = 2 * (4p + 3)

Hence, they cannot be prime numbers (since prime numbers must only be divisible by 1 and itself)

Only option B: 8p + 1 does not apparently have any factors
Thus, it is the only one that CAN BE prime (it might not be prime as well - we cannot ensure that it is prime)

Option B
Intern
Intern
Joined: 28 May 2020
Posts: 34
Own Kudos [?]: 36 [1]
Given Kudos: 369
Send PM
Re: If p is a positive integer, which of the following could be [#permalink]
1
8p = even integer
even + odd = odd
8p + 1 = odd integer

Answer B is the only choice that leads to an odd integer.

Also, 8(5) + 1 = 41
41 is a prime number
Prep Club for GRE Bot
Re: If p is a positive integer, which of the following could be [#permalink]
Moderators:
GRE Instructor
84 posts
GRE Forum Moderator
37 posts
Moderator
1111 posts
GRE Instructor
234 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne