GMAT Question of the Day: Daily via email | Daily via Instagram New to GMAT Club? Watch this Video
close
It is currently 01 Mar 2021, 23:58
Register
GMAT Club Tests
Decision Tracker
My Rewards
New posts
New comers' posts

Close

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
Your Progress

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

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

Go to My Error Log Learn more
Close

Request Expert Reply

Confirm Cancel
There are 20 cards in a box and each card is numbered from 1 to 20. Bi
10 posts Go to First Unread Post
Print view
NEW TOPIC
POST REPLY
Downloads
My Bookmarks
Reviews
SORT BY:
Date
Kudos
Tags:
Find Similar Topics 

Show Tags
Hide Tags

User avatar
V
Bunuel
Math Expert
Joined: 02 Sep 2009
Posts: 72189
CAT Tests Top Member of the Month
There are 20 cards in a box and each card is numbered from 1 to 20. Bi [#permalink] New post  27 Jan 2021, 12:35
5
Bookmarks
Expert Reply
00:00
A
B
C
D
E

Difficulty:

75% (hard)

Question Stats:

32% (01:34) correct 68% (01:46) wrong based on 53 sessions

Hide Show timer Statistics

There are 20 cards in a box and each card is numbered from 1 to 20. Bill picked cards at random from the box without replacement. What is the minimum number of cards drawn that will give a guaranteed even number for the sum of all the cards drawn?

A. 1
B. 3
C. 10
D. 12
E. 20

Are You Up For the Challenge: 700 Level Questions: 700 Level Questions
ShowHide Answer
Official Answer
Official Answer and Stats are available only to registered users. Register/Login.

_________________
New to the GMAT CLUB Forum?
Posting Rules: QUANTITATIVE | VERBAL. Guides and Resources: QUANTITATIVE | VERBAL | Ultimate GMAT Quantitative Megathread | All You Need for Quant

Questions' Banks and Collection:
PS: Standard deviation | Tough Problem Solving Questions With Solutions | Probability and Combinations Questions With Solutions | Tough and tricky exponents and roots questions | 12 Easy Pieces (or not?) | Bakers' Dozen | Algebra set | Mixed Questions | Fresh Meat
DS: DS Standard deviation | Inequalities | 700+ GMAT Data Sufficiency Questions With Explanations | Tough and tricky exponents and roots questions | The Discreet Charm of the DS | Devil's Dozen!!! | Number Properties set | New DS set
MIXED: GMAT Club's Complete Questions' Bank | SEVEN SAMURAI OF 2012 | Tricky questions from previous years. | Special Questions' Directory | Best Of The Best Of 2017 | The Best Of Quant of 2016 | 20 hardest and 20 best questions of 2015 | 15 best topics of 2015 | Seven Samurai of 2012 | GMAT Probability Questions

What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics
Signature Read More
User avatar
S
meanup
Senior Manager
Senior Manager
Joined: 15 Jun 2017
Posts: 463
Location: India
Re: There are 20 cards in a box and each card is numbered from 1 to 20. Bi [#permalink] New post  29 Jan 2021, 20:35
Based on the concept of Even and Odd number addition.

\(E+E =E\)
\(E+O=O =>O+O=E\)
\(O+O=E\)

Based on the above condition minimum number of cards to be drawn is \(3\) i.e. \(E+O+O=E\)

IMO Ans B
avatar
B
yatharthdas
Intern
Intern
Joined: 22 May 2019
Posts: 11
Re: There are 20 cards in a box and each card is numbered from 1 to 20. Bi [#permalink] New post  30 Jan 2021, 01:12
I think the answer is D
1 2 4 6 8 10 12 14 16 18 20 then u will use odd no. I.e. 3(or any other odd no.) Which will give the answer as even

Posted from my mobile device
avatar
G
Brian123
Manager
Manager
Joined: 05 Jul 2020
Posts: 211
GMAT 1: 720 Q49 V38
WE:Accounting (Accounting)
Reviews Badge
Re: There are 20 cards in a box and each card is numbered from 1 to 20. Bi [#permalink] New post  30 Jan 2021, 01:33
1
Kudos
The answer is E IMO.

For D, you can pick 9 Odd numbers (sum=odd) and 3 even numbers (sum=even). E+O will give you odd hence picking 12 won't suffice as it is possible to get an odd sum.

Picking 20 will definitely give you an even sum!
User avatar
S
rsrighosh
Manager
Manager
Joined: 13 Jun 2019
Posts: 111
GMAT 1: 490 Q42 V17
GMAT 2: 550 Q39 V27
Re: There are 20 cards in a box and each card is numbered from 1 to 20. Bi [#permalink] New post  30 Jan 2021, 05:59
I think answer is D
If we consider the worst case scenario

We pick 1st as Odd then next 10 even then 1 odd... So total is 12
_________________

Shrekey

Signature Read More
avatar
B
FAAS
Intern
Intern
Joined: 14 Oct 2020
Posts: 3
Re: There are 20 cards in a box and each card is numbered from 1 to 20. Bi [#permalink] New post  30 Jan 2021, 17:52
It has to be 20. Lets see for counter examples:

a) 1 drawn: 1 odd. --> sum is odd
b) 3 drawn: 1 odd +2 even --> sum is odd
c) 10 drawn: 9 even + 1 odd --> sum is odd
d) 12 drawn: 9 even + 3odd --> sum is odd

e) 20 dawn : 10 even + 10 odd --> sum is even (there is no other combination of cards, since the deck holds 20 cards only)

Answer E.
User avatar
S
twobagels
Manager
Manager
Joined: 12 Jul 2020
Posts: 60
Location: United States
There are 20 cards in a box and each card is numbered from 1 to 20. Bi [#permalink] New post  30 Jan 2021, 18:42
If you pull 1 then every even card in a row you'll get {1,2,4,6,8,10,12,14,16,18,20} then you'll need one more to get an even sum. That set is 11 integers, so I'd guess the answer is 12, because you'd have to pull one more card and it would be odd, since there are no evens left: hence 12 cards would be pulled and guarantee an even sum.

I venture to guess D.
avatar
B
elgunp
Intern
Intern
Joined: 09 Aug 2019
Posts: 5
Re: There are 20 cards in a box and each card is numbered from 1 to 20. Bi [#permalink] New post  01 Feb 2021, 08:14
E does not seem right. As mentioned above, if you select odd number of odds (e.g. 9 odds) then the sum is going to be odd (9 odds + 3 evens). Bunuel please explain why D is the right answer choice.
User avatar
V
Bunuel
Math Expert
Joined: 02 Sep 2009
Posts: 72189
CAT Tests Top Member of the Month
Re: There are 20 cards in a box and each card is numbered from 1 to 20. Bi [#permalink] New post  04 Feb 2021, 00:07
Expert Reply
Bunuel wrote:
There are 20 cards in a box and each card is numbered from 1 to 20. Bill picked cards at random from the box without replacement. What is the minimum number of cards drawn that will give a guaranteed even number for the sum of all the cards drawn?

A. 1
B. 3
C. 10
D. 12
E. 20

Are You Up For the Challenge: 700 Level Questions: 700 Level Questions


Anyone else want to try ?

Check other Worst Case Scenario Questions from our Special Questions Directory to practice.

Hope it helps.
_________________
New to the GMAT CLUB Forum?
Posting Rules: QUANTITATIVE | VERBAL. Guides and Resources: QUANTITATIVE | VERBAL | Ultimate GMAT Quantitative Megathread | All You Need for Quant

Questions' Banks and Collection:
PS: Standard deviation | Tough Problem Solving Questions With Solutions | Probability and Combinations Questions With Solutions | Tough and tricky exponents and roots questions | 12 Easy Pieces (or not?) | Bakers' Dozen | Algebra set | Mixed Questions | Fresh Meat
DS: DS Standard deviation | Inequalities | 700+ GMAT Data Sufficiency Questions With Explanations | Tough and tricky exponents and roots questions | The Discreet Charm of the DS | Devil's Dozen!!! | Number Properties set | New DS set
MIXED: GMAT Club's Complete Questions' Bank | SEVEN SAMURAI OF 2012 | Tricky questions from previous years. | Special Questions' Directory | Best Of The Best Of 2017 | The Best Of Quant of 2016 | 20 hardest and 20 best questions of 2015 | 15 best topics of 2015 | Seven Samurai of 2012 | GMAT Probability Questions

What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics
Signature Read More
avatar
B
wishmasterdj
Manager
Manager
Joined: 04 May 2016
Posts: 57
Location: India
Schools: ISB '18 (A)
GMAT 1: 700 Q48 V37
GPA: 3.2
Re: There are 20 cards in a box and each card is numbered from 1 to 20. Bi [#permalink] New post  20 Feb 2021, 01:58
rsrighosh wrote:
I think answer is D
If we consider the worst case scenario

We pick 1st as Odd then next 10 even then 1 odd... So total is 12


How about this case as worse than the one you just mentioned:

9 Odds, then 10 evens => sum is still odd

How do we counter that?
GMAT Club Bot
gmatclubot
[#permalink]
NEW TOPIC
POST REPLY
Downloads
My Bookmarks
Reviews
Moderators:
chetan2u
Math Expert
9507 posts
Bunuel
Math Expert
72189 posts
yashikaaggarwal
Senior Moderator - Masters Forum
2415 posts
generis
Senior SC Moderator
4550 posts
Feedback

cron

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

Main navigation

GMAT Resources

Partners

MBA Resources

www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions