Probalitiy Question

This topic has expert replies
Newbie | Next Rank: 10 Posts
Posts: 1
Joined: Thu Dec 30, 2010 4:44 am

Probalitiy Question

by daniel-fabry » Mon Jan 03, 2011 12:33 pm
There are 800 students at School Y. At the beginning of the first semester, 45% of the students have taken the math placement test, 15% have taken both the math and the verbal placement tests, and 10% have taken neither. By the end of the first semester, 60% of the students have taken the math placement test, 30% have taken both tests, and all students have taken at least one test. If no students have entered or left school Y, how many more students took the math placement test during the first semester than took the verbal placement test during the first semester?

How would you tackle this question

User avatar
Legendary Member
Posts: 543
Joined: Tue Jun 15, 2010 7:01 pm
Thanked: 147 times
Followed by:3 members

by anshumishra » Mon Jan 03, 2011 8:16 pm
daniel-fabry wrote:There are 800 students at School Y. At the beginning of the first semester, 45% of the students have taken the math placement test, 15% have taken both the math and the verbal placement tests, and 10% have taken neither. By the end of the first semester, 60% of the students have taken the math placement test, 30% have taken both tests, and all students have taken at least one test. If no students have entered or left school Y, how many more students took the math placement test during the first semester than took the verbal placement test during the first semester?

How would you tackle this question
You would normally make a venn diagram or a table. I am trying to put it here without diagram to show how it would look like. Hopefully, if there is no mistake, it should guide you to solve the problem.

Beginning of first sem :

Students who took Math Test -> 45%
Students who took both tests -> 15 % (that also means 30% only took Math test)
Students who took neither -> 10%
Hence, students who took verbal test -> 60% (that also means who took only verbal = 45%)

After first sem :

Students who took Math Test -> 60%
Students who took both tests -> 30 % (that also means 30% only took Math test)
Students who took neither -> 0%
Hence, students who took verbal test -> 70% (that also means who took only verbal = 40%)

So, we can see that 15% (60%-45%) more students took the math test, whereas only 10%(70%-60%) of the students took the verbal test.
So the difference is 5% = 800*5/100 = 40.
Thanks
Anshu

(Every mistake is a lesson learned )

User avatar
Community Manager
Posts: 1048
Joined: Mon Aug 17, 2009 3:26 am
Location: India
Thanked: 51 times
Followed by:27 members
GMAT Score:670

by arora007 » Mon Jan 10, 2011 10:20 am
at start M+MV =45% ( where MV =15)

at start (M +MV +V+10%) =100%
V=45 %
therefore now V +MV = 60%

at finish M +MV =60%

M+MV+V =100% (where MV =30 and M +MV =60%)
V=40%
V+MV=70%

question asked is what is diff between raise of M+MV and V+MV

for math the raise was from 45-->60 i.e 15%
for verbal the raise was from 60-->70-->10%

difference is 5% of 800 students which is 40 students...
https://www.skiponemeal.org/
https://twitter.com/skiponemeal
Few things are impossible to diligence & skill.Great works are performed not by strength,but by perseverance

pm me if you find junk/spam/abusive language, Lets keep our community clean!!

User avatar
Legendary Member
Posts: 1665
Joined: Thu Nov 03, 2011 7:04 pm
Thanked: 165 times
Followed by:70 members

by karthikpandian19 » Sat Jul 07, 2012 4:10 am
Nice twister in the last part of the sentence "how many more students took the math placement test during the first semester than took the verbal placement test during the first semester"

I misinterpreted the word translation here.
Regards,
Karthik
The source of the questions that i post from JUNE 2013 is from KNEWTON

---If you find my post useful, click "Thank" :) :)---
---Never stop until cracking GMAT---