GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 22 Feb 2019, 04:28

### GMAT 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

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

Practice
Pays

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

## Events & Promotions

###### Events & Promotions in February
PrevNext
SuMoTuWeThFrSa
272829303112
3456789
10111213141516
17181920212223
242526272812
Open Detailed Calendar
• ### Free GMAT RC Webinar

February 23, 2019

February 23, 2019

07:00 AM PST

09:00 AM PST

Learn reading strategies that can help even non-voracious reader to master GMAT RC. Saturday, February 23rd at 7 AM PT
• ### FREE Quant Workshop by e-GMAT!

February 24, 2019

February 24, 2019

07:00 AM PST

09:00 AM PST

Get personalized insights on how to achieve your Target Quant Score.

# How many prime factors of x are also prime factors of y?

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 53066
How many prime factors of x are also prime factors of y?  [#permalink]

### Show Tags

25 Jul 2016, 09:17
00:00

Difficulty:

35% (medium)

Question Stats:

66% (00:53) correct 34% (00:51) wrong based on 91 sessions

### HideShow timer Statistics

How many prime factors of x are also prime factors of y?

(1) x = 30
(2) y is a multiple of x

_________________
Intern
Joined: 22 Jul 2011
Posts: 21
Location: Bulgaria
Re: How many prime factors of x are also prime factors of y?  [#permalink]

### Show Tags

25 Jul 2016, 10:07
I picked C.

x=30 gives us the prime factors of x but does not establish a relationship with y. Insufficient.

y=kx means that y definitely shares all of x's prime factors. Pretty good but insufficient without a value for x.

Taking the two statements together, we know that x=30, and that y=k30, so y we can count how many prime factors 30 has. All of them y shares for sure. That's our answer.
Senior Manager
Joined: 02 Mar 2012
Posts: 297
Schools: Schulich '16
Re: How many prime factors of x are also prime factors of y?  [#permalink]

### Show Tags

25 Jul 2016, 23:48

1)insuff
2)ok. but what if x=0.then it shares 0 prime factors and if x=30 then 3, so This statement is insuff.

1+2,

yes it shares 3 factors(2,3,5)
Intern
Joined: 14 Jul 2016
Posts: 5
Re: How many prime factors of x are also prime factors of y?  [#permalink]

### Show Tags

26 Jul 2016, 01:44
hsbinfy wrote:

1)insuff
2)ok. but what if x=0.then it shares 0 prime factors and if x=30 then 3, so This statement is insuff.

1+2,

yes it shares 3 factors(2,3,5)

I will go for E.
it says y=kx
if k is a prime number then we wont be able to get any particular value for the number of prime numbers .
suppose k = 77 or k = 7*13*19 or etc
Manager
Joined: 07 Jul 2016
Posts: 78
GPA: 4
How many prime factors of x are also prime factors of y?  [#permalink]

### Show Tags

26 Jul 2016, 05:18
Bunuel wrote:
How many prime factors of x are also prime factors of y?

(1) x = 30
(2) y is a multiple of x

(1) x = 30

We do not know y

$$y = 30 \implies \text{shared prime factors} = \{2,5,3\}\\ y = 10 \implies \text{shared prime factors} = \{2,5\}$$

Insufficient

(2) y is a multiple of x

Neither x or y are fixed. Prove by example:

$$x = y = 2 \implies \text{shared prime factors} = \{2\}\\ x = y = 6 \implies \text{shared prime factors} = \{2,3\}$$

Insufficient

(1 AND 2).
We have $$x$$ fixed, and know that $$y$$ is a multiple of $$x$$.

For some multiple $$k \in \mathbb{Z}$$
$$y = kx$$.

Note that (2) does not state that the multiple must be positive.

$$k = 0 \implies \text{shared prime factors} = \varnothing\\ k \neq 0 \implies \text{shared prime factors} = \text{prime factors of 30} = \{2,3,5\}$$

Insufficient

(E) statements 1 and 2 together are not sufficient, and additional data is needed to answer the question

_________________

Please press +1 Kudos if this post helps.

Current Student
Joined: 12 Aug 2015
Posts: 2621
Schools: Boston U '20 (M)
GRE 1: Q169 V154
Re: How many prime factors of x are also prime factors of y?  [#permalink]

### Show Tags

21 Aug 2016, 07:53
here we arent asked the number of prime factors of y rather we are asked the number prime factors of that are also prime factors of x
statement 1 => insuff as there is no info on y
statement 2 => it tells us that all the prime factors of x must also be the prime factors of y (remember may contain additional prime factors as well but that isnt asked)
insuff
combining them as number od primes of x=3
hence y has all 3 primes of x and it may have even more
but it definitely has 2,3,5 as its prime factors
hence sufficient
SMASH that C
_________________
Non-Human User
Joined: 09 Sep 2013
Posts: 9887
Re: How many prime factors of x are also prime factors of y?  [#permalink]

### Show Tags

29 Jan 2019, 08:20
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
Re: How many prime factors of x are also prime factors of y?   [#permalink] 29 Jan 2019, 08:20
Display posts from previous: Sort by