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

 It is currently 18 Nov 2018, 22:00

### 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 November
PrevNext
SuMoTuWeThFrSa
28293031123
45678910
11121314151617
18192021222324
2526272829301
Open Detailed Calendar
• ### How to QUICKLY Solve GMAT Questions - GMAT Club Chat

November 20, 2018

November 20, 2018

09:00 AM PST

10:00 AM PST

The reward for signing up with the registration form and attending the chat is: 6 free examPAL quizzes to practice your new skills after the chat.
• ### The winning strategy for 700+ on the GMAT

November 20, 2018

November 20, 2018

06:00 PM EST

07:00 PM EST

What people who reach the high 700's do differently? We're going to share insights, tips and strategies from data we collected on over 50,000 students who used examPAL.

# If n and k are integers whose product is 400, which of the

Author Message
TAGS:

### Hide Tags

Manager
Joined: 16 Feb 2012
Posts: 178
Concentration: Finance, Economics
If n and k are integers whose product is 400, which of the  [#permalink]

### Show Tags

30 Jun 2012, 00:46
1
16
00:00

Difficulty:

65% (hard)

Question Stats:

58% (01:37) correct 42% (01:28) wrong based on 373 sessions

### HideShow timer Statistics

If n and k are integers whose product is 400, which of the following statements must be true?

A. n + k > 0
B. n is not equal to k.
C. Either n or k is a multiple of 10.
D. If n is even, then k is odd.
E. If n is odd, then k is even.

_________________

Kudos if you like the post!

Failing to plan is planning to fail.

Math Expert
Joined: 02 Sep 2009
Posts: 50627
Re: If n and k are integers whose product is 400, which of the f  [#permalink]

### Show Tags

30 Jun 2012, 02:22
2
4
If n and k are integers whose product is 400, whcih of the following statements must be true?

Note that the question is: "whcih of the following must be true?"

Given: $$nk=400$$

For the product of two integers to be even at least one integer must be even.

A. n+k>0 --> not necessarily true: $$nk=(-20)*(-20)=400$$;
B. n does not equal k --> not necessarily true: $$nk=20*20=400$$;
C. Either n or k is a multiple of 10 --> not necessarily true: $$nk=16*25=400$$.
D. If n is even, then k is odd --> not necessarily true, $$n$$ can be even and $$k$$ be even too --> $$nk=20*20=400$$;
E. If n is odd, then k is even --> this must be true, if one of the factors is odd ($$n$$) the second one ($$k$$) must be even for their product to be even.

Hope it's clear.
_________________
##### General Discussion
Intern
Status: Trying to crack GMAT
Joined: 17 May 2012
Posts: 30
Location: India
Concentration: Operations, Technology
GMAT Date: 07-11-2012
GPA: 3.82
WE: Engineering (Computer Software)
Re: If n and k are integers whose product is 400, which of the  [#permalink]

### Show Tags

01 Jul 2012, 20:58
Ohh..this one was really fun..got screwed up btw D and E. Didn't read between the lines. Thanks for explaining Bunuel.
_________________

“When I was young I observed that nine out of ten things I did were failures, so I did ten times more work.” ~ Bernard Shaw

Kudos me if I helped you in any way.

Director
Joined: 08 Jun 2010
Posts: 906
Re: If n and k are integers whose product is 400, which of the  [#permalink]

### Show Tags

05 May 2015, 23:19
Bunuel wrote:
If n and k are integers whose product is 400, whcih of the following statements must be true?

Note that the question is: "whcih of the following must be true?"

Given: $$nk=400$$

For the product of two integers to be even at least one integer must be even.

A. n+k>0 --> not necessarily true: $$nk=(-20)*(-20)=400$$;
B. n does not equal k --> not necessarily true: $$nk=20*20=400$$;
C. Either n or k is a multiple of 10 --> not necessarily true: $$nk=16*25=400$$.
D. If n is even, then k is odd --> not necessarily true, $$n$$ can be even and $$k$$ be even too --> $$nk=20*20=400$$;
E. If n is odd, then k is even --> this must be true, if one of the factors is odd ($$n$$) the second one ($$k$$) must be even for their product to be even.

Hope it's clear.

I need just to know that if n is odd, k is even. this is enough to tick e. no need explanation more.
Director
Joined: 08 Jun 2010
Posts: 906
Re: If n and k are integers whose product is 400, which of the  [#permalink]

### Show Tags

12 May 2015, 01:38
Bunuel wrote:
If n and k are integers whose product is 400, whcih of the following statements must be true?

Note that the question is: "whcih of the following must be true?"

Given: $$nk=400$$

For the product of two integers to be even at least one integer must be even.

A. n+k>0 --> not necessarily true: $$nk=(-20)*(-20)=400$$;
B. n does not equal k --> not necessarily true: $$nk=20*20=400$$;
C. Either n or k is a multiple of 10 --> not necessarily true: $$nk=16*25=400$$.
D. If n is even, then k is odd --> not necessarily true, $$n$$ can be even and $$k$$ be even too --> $$nk=20*20=400$$;
E. If n is odd, then k is even --> this must be true, if one of the factors is odd ($$n$$) the second one ($$k$$) must be even for their product to be even.

Hope it's clear.

in the test room, we can not find 25x16=400 easily. so, if we see E, if n is odd then k is even

tick choice E. that is done.
SVP
Joined: 06 Nov 2014
Posts: 1882
Re: If n and k are integers whose product is 400, which of the  [#permalink]

### Show Tags

12 May 2015, 03:40
If n and k are integers whose product is 400, which of the following statements must be true?

A.n + k > 0 n and k should have the same sign, but that means that they can also both be negative
B.n is not equal to k. 20 x 20 = 400[i]
C. Either n or k is a multiple of 10. [i]25 x 16 = 400

D. If n is even, then k is odd. k can also be even since even x even will be even
E. If n is odd, then k is even. k must be even since odd x even = even
Target Test Prep Representative
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 2830
Re: If n and k are integers whose product is 400, which of the  [#permalink]

### Show Tags

17 May 2018, 17:02
Stiv wrote:
If n and k are integers whose product is 400, which of the following statements must be true?

A. n + k > 0
B. n is not equal to k.
C. Either n or k is a multiple of 10.
D. If n is even, then k is odd.
E. If n is odd, then k is even.

Since an even product must contain at least 1 even number in the multiplication, if n is odd, then k must be even.

If you had difficulty differentiating between choices D and E, consider the wording. Choice D states that if we are given that n is even, then k must be odd, which is not necessarily true, because k could be even. Take n = 20 and k = 20 for instance (which also eliminates answer choice B). However, Choice E states that if we are given that n is odd, then k must be even. This is a true statement, because the product nk is even.

_________________

Jeffery Miller

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Senior Manager
Joined: 29 Jun 2017
Posts: 428
Re: If n and k are integers whose product is 400, which of the  [#permalink]

### Show Tags

14 Sep 2018, 00:29
we should begin with 400=2^2*5^2*2^2

from this we see that all condition except choice E can be correct but must not be correct.
Re: If n and k are integers whose product is 400, which of the &nbs [#permalink] 14 Sep 2018, 00:29
Display posts from previous: Sort by