BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Target Test Prep · GMAT

Choose how you want to prepare

Learn live with an expert or move at your own pace. Every option includes the complete TTP study system.

★★★★★5.0559 reviews
GMATLiveTeach Starts Oct 17
Chris Peckover, Target Test Prep GMAT expert
LIVE ONLINE CLASSES

Get Ready for GMAT Test Day Faster with Live Online Classes

with Chris Peckover, 100th-Percentile GMAT Scorer

Oct 17 · Chris Peckover
Sat · 11:00 AM to 2:00 PM ET
Oct 20 · Chris Peckover
Tue, Thu · 8:00 to 10:00 PM ET
Oct 25 · Josh Braslow
Sun · 1:00 to 4:00 PM ET
Included
40 hours of live online classes + 6 months of TTP OnDemand
  • Attend the first class for free
  • Every class is recorded, so you never fall behind
View classes & enroll
Limited seats availableTarget Test Prep
EALiveTeachOnDemand 5 seats left Start anytime
EXECUTIVE ASSESSMENT

Target Test Prep EA OnDemand

Self-paced EA prep. Study on your schedule.

Logan Thompson
EXECUTIVE ASSESSMENT

Sep 6 to Dec 6, 2026

with Logan Thompson

165+ EA score guarantee
$05-day trial no automatic billing
Schedule
Sun · 9:30 AM to 12:30 PM ET
Included
40 hours of live online classes plus six months of access to the complete TTP EA OnDemand course.
  • 165+ EA Score Guarantee
  • 4,100+ Quant, Verbal, and Integrated Reasoning practice questions
  • 400+ hours of in-depth video lessons
  • 3,000+ step-by-step video solutions
View EA class & enroll Start free 5-day trial
Limited cohort · enrollment openTrial includes full course accessTarget Test Prep
GMATOnDemand Start anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

715+ score guarantee
$0to start then $127/mo
  • Personalized study plan and analytics
  • Thousands of lessons and practice questions
Start free 5-day trial
Read 559 reviewsTarget Test Prep

Compare the format, schedule, and included access before enrolling. Prices and seat counts shown reflect the supplied offer details.

science books

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 447
Joined: Sun Apr 19, 2009 9:08 pm
Location: Kolkata,India
Thanked: 7 times
GMAT Score:670
by uptowngirl92 » Sat Jun 06, 2009 4:10 am
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

[spoiler]OA:E[/spoiler]

help guys!Detailed explanation needed!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
User avatar
Site Admin
Posts: 2567
Joined: Thu Jan 01, 2009 10:05 amFollowed by: 550 members
Thanked: 712 times
GMAT Score:770

by DanaJ » Sat Jun 06, 2009 5:56 am
This is a worst case scenario question.

Consider you're the unluckiest person in the world: then when you take some books out of the library, it just so happens that they're all from the sets that DON'T have at least 80 books, which means that you take out 50 + 50 + 65 = 165 books with no success. Then you start on the other two sets. You might think that taking an extra 80 books out will suffice, but what if you take 40 out of the physics books and 40 out of the chemistry books? To be 100% sure you've taken at least 80 books from one subject, you need to take out another 80 + 79 = 159 books. This way, you're absolutely sure you've gotten the required quota out of there.

Take less than 159 books out of there, and you might be carrying 79 books of one subject and 79 books of the other. But take the 159 and you're 100% sure you've taken at least 80 books of the same subject.

The grand total will be 165 + 159 = 324.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 447
Joined: Sun Apr 19, 2009 9:08 pm
Location: Kolkata,India
Thanked: 7 times
GMAT Score:670

by uptowngirl92 » Wed Jun 10, 2009 9:33 pm
DanaJ wrote:. Then you start on the other two sets. You might think that taking an extra 80 books out will suffice, but what if you take 40 out of the physics books and 40 out of the chemistry books? To be 100% sure you've taken at least 80 books from one subject, you need to take out another 80 + 79 = 159 books. This way, you're absolutely sure you've gotten the required quota out of there.

Take less than 159 books out of there, and you might be carrying 79 books of one subject and 79 books of the other. But take the 159 and you're 100% sure you've taken at least 80 books of the same subject.

The grand total will be 165 + 159 = 324.
I did'nt understand the last part.Where did the 79 come from??
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 752
Joined: Sun May 17, 2009 11:04 pm
Location: Tokyo
Thanked: 81 times
GMAT Score:680

by tohellandback » Thu Jun 11, 2009 12:53 am
This is more of a reasoning question than maths..
we want to know how many books MUST be removed to ensure that 80 of the books removed are on the same science. so we have to take the worst case.
Now botany,zoology and geology books are less than 80 in number. we are looking for worst case, so let's say we are running a bad luck and we get them first
.so 50+50+50
now lets say we got 79 physics books and our luck is so bad that we don't get the 80th one(worst case,remember?). thats why we add 79 here. same for the chemistry books
after this whatever book we get, it will complete 80 books of the same color condition
so 1 here
total=50+50+65+79+79+1
hope i helped
The powers of two are bloody impolite!!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1