Last visit was: 25 Nov 2024, 08:13 It is currently 25 Nov 2024, 08:13

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: 30022
Own Kudos [?]: 36391 [0]
Given Kudos: 25928
Send PM
Verbal Expert
Joined: 18 Apr 2015
Posts: 30022
Own Kudos [?]: 36391 [0]
Given Kudos: 25928
Send PM
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Own Kudos [?]: 12197 [0]
Given Kudos: 136
Send PM
User avatar
Senior Manager
Senior Manager
Joined: 10 Feb 2020
Posts: 496
Own Kudos [?]: 350 [0]
Given Kudos: 299
Send PM
Re: If an integer is divisible by both 27 and 10, then the [#permalink]
GreenlightTestPrep wrote:
Carcass wrote:
If an integer is divisible by both 27 and 10, then the integer also must be divisible by which of the following?

A. 4
B. 25
C. 36
D. 54
E. 81


-----ASIDE---------------------
A lot of integer property questions can be solved using prime factorization.
For questions involving divisibility, divisors, factors and multiples, we can say:
If N is divisible by k, then k is "hiding" within the prime factorization of N

Consider these examples:
24 is divisible by 3 because 24 = (2)(2)(2)(3)
Likewise, 70 is divisible by 5 because 70 = (2)(5)(7)
And 112 is divisible by 8 because 112 = (2)(2)(2)(2)(7)
And 630 is divisible by 15 because 630 = (2)(3)(3)(5)(7)
-----ONTO THE QUESTION!---------------------

Let's say the integer in question is N

The integer (N) is divisible by 27
27 = (3)(3)(3)
So, we can say N = (3)(3)(3)(?)(?)...

Aside: the other ?'s represents other possible prime numbers in the prime factorization of N

The integer (N) is divisible by 10
10 = (2)(5)
So, we can say N = (2)(5)(?)(?)...

When we combine both pieces of information we can write: N = (3)(3)(3)(2)(5)(?)(?)

The integer (N) also must be divisible by which of the following?
N = (3)(3)(3)(2)(5)(?)(?)

A. 4
4 = (2)(2)
Since the prime factorization of N (above) does NOT include two 2's, it need not be the case that N is divisible by 4
Eliminate A

B. 25
25 = (5)(5)
Since the prime factorization of N (above) does NOT include two 5's, it need not be the case that N is divisible by 25
Eliminate B

C. 36
36 = (2)(2)(3)(3)
Since the prime factorization of N (above) does NOT include two 2's and two 3's, it need not be the case that N is divisible by 36
Eliminate C

D. 54
54 = (2)(3)(3)(3)
Since the prime factorization of N (above) DOES include one 2 and three 3's, we can be certain that N is divisible by 54


Answer: D


But we wont consider 5?
avatar
Manager
Manager
Joined: 08 Aug 2020
Posts: 92
Own Kudos [?]: 108 [0]
Given Kudos: 0
Send PM
Re: If an integer is divisible by both 27 and 10, then the [#permalink]
2
This how I did mine
For a number to be divisible by 27 and 10 then the smallest number it can be will be 270(multiply)

Then I started dividing each option with 270 till I got D

Posted from my mobile device Image
avatar
Intern
Intern
Joined: 25 Aug 2020
Posts: 17
Own Kudos [?]: 13 [0]
Given Kudos: 0
Send PM
Re: If an integer is divisible by both 27 and 10, then the [#permalink]
1
Hi!

The first thing that should pop out to you when looking at these kinds of questions is "what's similar between these values?". I knew to find the Least Common Multiple of both of them since their individual factors have nothing in common with eachother. Multiplying 27*10=270. From there I decided to find a factor of 270 and found that 54 was the only value that gave me a whole number, thus answer choice D. Cheers! :shock:
Prep Club for GRE Bot
Re: If an integer is divisible by both 27 and 10, then the [#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