Of the science books in a certain supply room, 50 are on : GMAT Problem Solving (PS)
Check GMAT Club Decision Tracker for the Latest School Decision Releases https://gmatclub.com/AppTrack

 It is currently 28 Feb 2017, 07:52

### 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 June
Open Detailed Calendar

# Of the science books in a certain supply room, 50 are on

Author Message
TAGS:

### Hide Tags

Senior Manager
Status: May The Force Be With Me (D-DAY 15 May 2012)
Joined: 06 Jan 2012
Posts: 289
Location: India
Concentration: General Management, Entrepreneurship
Followers: 3

Kudos [?]: 265 [6] , given: 16

Of the science books in a certain supply room, 50 are on [#permalink]

### Show Tags

21 Apr 2012, 20:17
6
KUDOS
17
This post was
BOOKMARKED
00:00

Difficulty:

65% (hard)

Question Stats:

61% (02:28) correct 39% (01:59) wrong based on 361 sessions

### HideShow timer Statistics

Of the science books in a certain supply room, 50 are on botany, 65 are on zoology, 90 are on physics. 50 are on geology, and 110 are on chemistry. If science books are removed randomly from the supply room, how many must be removed to ensure that 80 of the books removed are on the same science?

A. 81
B. 159
C. 166
D. 285
E. 324
[Reveal] Spoiler: OA

_________________

Giving +1 kudos is a better way of saying 'Thank You'.

Math Expert
Joined: 02 Sep 2009
Posts: 37154
Followers: 7278

Kudos [?]: 96863 [8] , given: 10808

Of the science books in a certain supply room, 50 are on [#permalink]

### Show Tags

21 Apr 2012, 21:11
8
KUDOS
Expert's post
11
This post was
BOOKMARKED
boomtangboy wrote:
16. Of the science books in a certain supply room, 50 are on botany, 65 are on zoology, 90 are on physics, 50 are on geology, and 110 are on chemistry. If science books are removed randomly from the supply room, how many must be removed to ensure that 80 of the books removed are on the same science?

(A) 81
(B) 159
(C) 166
(D) 285
(E) 324

We can remove 80 books only from physics or from chemistry. Worst case scenario would be if we remove all books on botany, zoology, geology, 79 books on physics and 79 books on chemistry.

We would have 50(botany) + 65(zoology) + 50(geology) + 79(physics) + 79(chemistry) = 323 books and still won't have 80 books from the same science. As after this, only books on physics and chemistry will be left then any next book would become the 80th book either on physics or on chemistry.

Similar questions to practice:
12-easy-pieces-or-not-126366.html#p1033935
in-his-pocket-a-boy-has-3-red-marbles-4-blue-marbles-and-85216.html
of-the-science-books-in-a-certain-supply-room-50-are-on-131100.html
in-a-deck-of-52-cards-each-card-is-one-of-4-different-color-83183.html
a-box-contains-10-red-pills-5-blue-pills-12-yellow-56779.html
each-of-the-integers-from-0-to-9-inclusive-is-written-on-130562.html

Hope it helps.
_________________
Intern
Joined: 01 Aug 2011
Posts: 23
Followers: 0

Kudos [?]: 7 [0], given: 15

Re: Of the science books in a certain supply room, 50 are on [#permalink]

### Show Tags

22 Apr 2012, 00:15
Thanks Bunel. Very helpful response yet again!

Is this the only way to solve this?
Math Expert
Joined: 02 Sep 2009
Posts: 37154
Followers: 7278

Kudos [?]: 96863 [1] , given: 10808

Re: Of the science books in a certain supply room, 50 are on [#permalink]

### Show Tags

22 Apr 2012, 00:21
1
KUDOS
Expert's post
shreya717 wrote:
Thanks Bunel. Very helpful response yet again!

Is this the only way to solve this?

Pretty much yes. For such kind of questions you should test worst case scenario to get the answer. Check the links in my previous post for similar questions.
_________________
Math Expert
Joined: 02 Sep 2009
Posts: 37154
Followers: 7278

Kudos [?]: 96863 [0], given: 10808

Re: Of the science books in a certain supply room, 50 are on [#permalink]

### Show Tags

14 Jun 2013, 04:29
Bumping for review and further discussion*. Get a kudos point for an alternative solution!

*New project from GMAT Club!!! Check HERE

All DS Min/Max Problems to practice: search.php?search_id=tag&tag_id=42
All PS Min/Max Problems to practice: search.php?search_id=tag&tag_id=63

_________________
GMAT Club Legend
Joined: 09 Sep 2013
Posts: 14002
Followers: 592

Kudos [?]: 168 [0], given: 0

Re: Of the science books in a certain supply room, 50 are on [#permalink]

### Show Tags

04 Sep 2014, 16:29
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.
_________________
Math Expert
Joined: 02 Sep 2009
Posts: 37154
Followers: 7278

Kudos [?]: 96863 [0], given: 10808

Re: Of the science books in a certain supply room, 50 are on [#permalink]

### Show Tags

20 Jan 2015, 12:12
Expert's post
1
This post was
BOOKMARKED
boomtangboy wrote:
Of the science books in a certain supply room, 50 are on botany, 65 are on zoology, 90 are on physics. 50 are on geology, and 110 are on chemistry. If science books are removed randomly from the supply room, how many must be removed to ensure that 80 of the books removed are on the same science?

A. 81
B. 159
C. 166
D. 285
E. 324

Check other Worst Case Scenario Questions from our Special Questions Directory.
_________________
Senior Manager
Joined: 10 Mar 2013
Posts: 291
GMAT 1: 620 Q44 V31
GMAT 2: 690 Q47 V37
GMAT 3: 610 Q47 V28
GMAT 4: 700 Q50 V34
GMAT 5: 700 Q49 V36
GMAT 6: 690 Q48 V35
GMAT 7: 750 Q49 V42
GMAT 8: 730 Q50 V39
Followers: 10

Kudos [?]: 100 [0], given: 2405

Of the science books in a certain supply room, 50 are on [#permalink]

### Show Tags

17 Dec 2015, 07:22
Bunuel wrote:
boomtangboy wrote:
16. Of the science books in a certain supply room, 50 are on botany, 65 are on zoology, 90 are on physics, 50 are on geology, and 110 are on chemistry. If science books are removed randomly from the supply room, how many must be removed to ensure that 80 of the books removed are on the same science?

(A) 81
(B) 159
(C) 166
(D) 285
(E) 324

We can remove 80 books only from physics or from chemistry. Worst case scenario would be if we remove all books on botany, zoology, geology, 79 books on physics and 79 books on chemistry.

We would have 50(botany) + 65(zoology) + 50(geology) + 79(physics) + 79(chemistry) = 323 books and still won't have 80 books from the same science. As after this, only books on physics and chemistry will be left then any next book would become the 80th book either on physics or on chemistry.

Similar questions to practice:
12-easy-pieces-or-not-126366.html#p1033935
in-his-pocket-a-boy-has-3-red-marbles-4-blue-marbles-and-85216.html
of-the-science-books-in-a-certain-supply-room-50-are-on-131100.html
in-a-deck-of-52-cards-each-card-is-one-of-4-different-color-83183.html
a-box-contains-10-red-pills-5-blue-pills-12-yellow-56779.html
each-of-the-integers-from-0-to-9-inclusive-is-written-on-130562.html

Hope it helps.

Bunuel, you used the URL to the solution of the problem listed here: 12-easy-pieces-or-not-126366.html#p1033935 rather than to the problem itself.
Intern
Joined: 31 Oct 2015
Posts: 37
Followers: 0

Kudos [?]: 2 [0], given: 53

Of the science books in a certain supply room, 50 are on [#permalink]

### Show Tags

03 Jan 2016, 11:44
What is the number at which picking one more book will guarantee that a thresold of 80 has been surpassed in one science?

Imagine you are playing a rigged game. The object of the game is for you to draw 80 books from the same science. The person attempting to cheat you out of winning picks out the books for you. He or she tries to prevent you from drawing the winning number of books until it is no longer possible to do so. He or she first starts off by picking books that cannot reach the 80 threshold and does so until such books are exhausted. He or she then starts picking books out of one the two remaining sciences until he reaches 79. To delay reaching the 80 thresold as much as possible he or she then shifts to the last science until he or she reaches 79. At this point it is no longer possible to cheat you out of winning and when the next book is drawn, you meet the 80 book threshold. The number of books drawn at that point is therefore 50 + 65 + 50 + 79 + 79 + 1 = 324.
Intern
Joined: 06 Oct 2014
Posts: 14
Concentration: Finance
GMAT 1: 700 Q45 V41
GPA: 3.8
Followers: 0

Kudos [?]: 7 [0], given: 24

Re: Of the science books in a certain supply room, 50 are on [#permalink]

### Show Tags

09 May 2016, 15:02

You know that only books you can remove to get 80 of the same science is Physics (90) or Chemistry (110). Probability of drawing out a Chemistry is higher with every draw 110/365 vs 80/365. Logically you'll need to take out fewer books to 80 of the Chemistry. So you look at Physics books instead. Because the question says 'ensure'.

P(Physics) = 90/365 simplify to 90/360 or 1/4. You know that for every 4 books you take out 1 is likely to be a physics book. Then to get 80 physics books you need to take out 80 x 4 = 320. Answer is (E)
Intern
Joined: 22 Apr 2016
Posts: 1
Followers: 0

Kudos [?]: 1 [1] , given: 0

Re: Of the science books in a certain supply room, 50 are on [#permalink]

### Show Tags

11 May 2016, 19:31
1
KUDOS
[quote="Bunuel"]Bumping for review and further discussion*. Get a kudos point for an alternative solution!

To ensure you get at least 80 books, you only look at Physics or Chemistry. 90 or 110. I calculated what percentage 80 books were of each group and took the highest percentage (i.e. 80/90 for Physics) and multiplied it by the total number of books (365). This makes sure you get 80 of one science as it makes sure you get 80 of the science that has the fewer books (i.e. harder probability). This gives you exactly 324.
Re: Of the science books in a certain supply room, 50 are on   [#permalink] 11 May 2016, 19:31
Similar topics Replies Last post
Similar
Topics:
4 On a Saturday night, each of the rooms at a certain motel was rented 2 11 Nov 2015, 00:01
8 A certain hotel has 1,400 single rooms and 420 double rooms. Each room 3 10 Nov 2015, 23:49
11 In the storage room of a certain bakery, the ratio of sugar 6 20 Jan 2013, 13:42
1 Science books....confusing question 6 04 Apr 2011, 05:53
18 If a librarian randomly removes science books from a library 9 08 May 2010, 08:54
Display posts from previous: Sort by