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

 It is currently 22 Aug 2018, 00:54

### 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

# If k is the smallest positive integer such that 2,940k

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:

### Hide Tags

Intern
Joined: 16 Feb 2013
Posts: 6
If k is the smallest positive integer such that 2,940k  [#permalink]

### Show Tags

04 May 2013, 10:17
4
00:00

Difficulty:

35% (medium)

Question Stats:

71% (01:35) correct 29% (01:40) wrong based on 166 sessions

### HideShow timer Statistics

If k is the smallest positive integer such that 2,940k is the square of an integer, then k must be

A. 3
B. 5
C. 6
D. 15
E. 21
Intern
Joined: 23 Apr 2013
Posts: 21
Re: If k is the smallest positive integer such that 2,940k  [#permalink]

### Show Tags

04 May 2013, 10:52
1
streamingline wrote:
If k is the smallest positive integer such that 2,940k is the square of an integer, then k must be

A)3
B)5
C)6
D)15
E)21

Spoiler: :: OA
15

$$2940 = 2^2 * 3 * 5 * 7^2$$

So the smallest positive integer to be multiplied to make it a perfect square is 3 * 5 = 15

Correct Option is D
Intern
Joined: 16 Feb 2013
Posts: 6
Re: If k is the smallest positive integer such that 2,940k  [#permalink]

### Show Tags

04 May 2013, 19:35
Thanks, didn't realise K was multiplied by 2940
Manager
Joined: 03 Aug 2015
Posts: 56
Concentration: Strategy, Technology
Schools: ISB '18, SPJ GMBA '17
GMAT 1: 680 Q48 V35
Re: If k is the smallest positive integer such that 2,940k  [#permalink]

### Show Tags

11 Jan 2016, 08:23
streamingline wrote:
If k is the smallest positive integer such that 2,940k is the square of an integer, then k must be

A. 3
B. 5
C. 6
D. 15
E. 21

Hi,

Pls clarify whether K is a unit digit of the given No. or it is in multiplication?
Math Expert
Joined: 02 Sep 2009
Posts: 48119
Re: If k is the smallest positive integer such that 2,940k  [#permalink]

### Show Tags

11 Jan 2016, 08:24
ArunpriyanJ wrote:
streamingline wrote:
If k is the smallest positive integer such that 2,940k is the square of an integer, then k must be

A. 3
B. 5
C. 6
D. 15
E. 21

Hi,

Pls clarify whether K is a unit digit of the given No. or it is in multiplication?

It's a multiplication sign.
_________________
SC Moderator
Joined: 22 May 2016
Posts: 1916
If k is the smallest positive integer such that 2,940k  [#permalink]

### Show Tags

06 Jul 2018, 10:04
1
streamingline wrote:
If k is the smallest positive integer such that 2,940k is the square of an integer, then k must be

A. 3
B. 5
C. 6
D. 15
E. 21

• Perfect square rule: A perfect square always has an even number of powers of prime factors.
That rule is often easier to remember this way:
all prime factors must come in pairs. Couplets.

There are no single "copies" of a prime factor in a perfect square.
If there is only one "copy" of a prime factor, or an odd number of copies, then the integer is not a perfect square.

• $$2,940 * k$$ is a perfect square

Prime factorize: $$2,940= 2 * 2 *3*5*7*7$$
This situation will not make a perfect square.
The 3s and the 5s are not in pairs. We need one more copy of each.
(We have $$3^1$$ and $$5^1$$, but exponents on prime factors must be even.)

$$k$$ is the number that provides the extra $$3$$ and the extra $$5$$
$$k = 3*5 = 15$$

$$2,940 * (3*5) = 44,100$$, which is $$210^2$$
_________________

In the depths of winter, I finally learned
that within me there lay an invincible summer.

If k is the smallest positive integer such that 2,940k &nbs [#permalink] 06 Jul 2018, 10:04
Display posts from previous: Sort by

# If k is the smallest positive integer such that 2,940k

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics

# Events & Promotions

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.