Of the science books in a certain supply room, 50 are on : PS Archive
Check GMAT Club App Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 08 Dec 2016, 22:42

### 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
Manager
Joined: 05 Sep 2007
Posts: 144
Location: New York
Followers: 1

Kudos [?]: 36 [0], given: 0

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

### Show Tags

22 Mar 2008, 14:50
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions

### HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

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
Senior Manager
Joined: 01 Feb 2005
Posts: 274
Followers: 2

Kudos [?]: 88 [0], given: 1

### Show Tags

22 Mar 2008, 17:09
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

From the question if we need 80 of one kind, botany, zoology and geology are out of the race. Physics and Chemistry are the ones remaining. if I remove 80 books of physics out of 90 then I have 10 remaining. Similarly if I removed 80 chemistry books then I have 30 remaining. So I add up the 10 + 30 = 40 books. However if I got 80 of the physics books then I have 31 of the chemistry books left and vice versa. So the total is 10 +31 = 41 or 11 + 30 = 41.

Subtract the total 365 - 41 = 324. Answer is E.
Senior Manager
Joined: 24 Feb 2008
Posts: 348
Schools: UCSD ($) , UCLA, USC ($), Stanford
Followers: 184

Kudos [?]: 2854 [0], given: 2

### Show Tags

22 Mar 2008, 17:13
axl_oz 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

From the question if we need 80 of one kind, botany, zoology and geology are out of the race. Physics and Chemistry are the ones remaining. if I remove 80 books of physics out of 90 then I have 10 remaining. Similarly if I removed 80 chemistry books then I have 30 remaining. So I add up the 10 + 30 = 40 books. However if I got 80 of the physics books then I have 31 of the chemistry books left and vice versa. So the total is 10 +31 = 41 or 11 + 30 = 41.

Subtract the total 365 - 41 = 324. Answer is E.

You are correct!

Forget about a stupid reunion. Bring on CD!
_________________

Best AWA guide here: http://gmatclub.com/forum/how-to-get-6-0-awa-my-guide-64327.html

Manager
Joined: 05 Sep 2007
Posts: 144
Location: New York
Followers: 1

Kudos [?]: 36 [0], given: 0

### Show Tags

22 Mar 2008, 18:04
how did you get 41? could you please clarify "if I got 80 of the physics books then I have 31 of the chemistry books left and vice versa. So the total is 10 +31 = 41 or 11 + 30 = 41."
Manager
Joined: 02 Mar 2008
Posts: 210
Concentration: Finance, Strategy
Followers: 1

Kudos [?]: 45 [0], given: 1

### Show Tags

22 Mar 2008, 18:50
i don't understand the above explanation also.
Using pigeon hole theory, left Phy and Chem, need to take out to ensure at least 80 bks on same topic
-> 79+80=159
plus the rest get E
SVP
Joined: 04 May 2006
Posts: 1926
Schools: CBS, Kellogg
Followers: 22

Kudos [?]: 985 [0], given: 1

### Show Tags

22 Mar 2008, 19:12
I definitely dont understand the logic of this kind problem. Can you guys mind giving detail of this logic? Your support is appreciated!
_________________
Manager
Joined: 21 Mar 2007
Posts: 73
Followers: 1

Kudos [?]: 76 [1] , given: 0

### Show Tags

23 Mar 2008, 05:34
1
KUDOS
el1981 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

E

When you asked "how many must be removed," it means the same thing as "how many must you takeout to GUARANTEE that 80 books on the same science" are removed.

In order for there to be a GUARANTEE that you will get 80 books on the same science (either physics or chemistry) you must take out 50 + 50 + 65 + 79 (of either physics or chem) + 80 (either physics or chem) = 324.

When you take out 79 of either physics or chem, the next 80 GUARANTEES that you will have 80 books on the same science.

Hope this helps!
CEO
Joined: 17 Nov 2007
Posts: 3589
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 530

Kudos [?]: 3456 [0], given: 360

### Show Tags

23 Mar 2008, 07:05
sondenso wrote:
I definitely dont understand the logic of this kind problem. Can you guys mind giving detail of this logic? Your support is appreciated!

Do you remember candies? the logic here is very close to the problem about 90 candies....
_________________

HOT! GMAT TOOLKIT 2 (iOS) / GMAT TOOLKIT (Android) - The OFFICIAL GMAT CLUB PREP APP, a must-have app especially if you aim at 700+ | PrepGame

SVP
Joined: 04 May 2006
Posts: 1926
Schools: CBS, Kellogg
Followers: 22

Kudos [?]: 985 [0], given: 1

### Show Tags

23 Mar 2008, 18:37
walker wrote:
sondenso wrote:
I definitely dont understand the logic of this kind problem. Can you guys mind giving detail of this logic? Your support is appreciated!

Do you remember candies? the logic here is very close to the problem about 90 candies....

I had reached this problem before I got the candies.

Many thanks to Japped187 and Walker!
_________________
Re: PS: Science books   [#permalink] 23 Mar 2008, 18:37
Display posts from previous: Sort by