GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 23 Feb 2019, 05:52

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.

Close

Request Expert Reply

Confirm Cancel
Events & Promotions in February
PrevNext
SuMoTuWeThFrSa
272829303112
3456789
10111213141516
17181920212223
242526272812
Open Detailed Calendar
  • Free GMAT RC Webinar

     February 23, 2019

     February 23, 2019

     07:00 AM PST

     09:00 AM PST

    Learn reading strategies that can help even non-voracious reader to master GMAT RC. Saturday, February 23rd at 7 AM PT
  • FREE Quant Workshop by e-GMAT!

     February 24, 2019

     February 24, 2019

     07:00 AM PST

     09:00 AM PST

    Get personalized insights on how to achieve your Target Quant Score.

A box has some red and some green balls in it. There are no balls of

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

 
Manager
Manager
User avatar
G
Joined: 31 Aug 2016
Posts: 223
Location: India
Concentration: Operations, Finance
GMAT 1: 680 Q49 V33
GMAT 2: 700 Q49 V37
GPA: 2.81
Premium Member Reviews Badge
A box has some red and some green balls in it. There are no balls of  [#permalink]

Show Tags

New post 30 Sep 2018, 17:33
1
2
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

82% (01:21) correct 18% (01:02) wrong based on 134 sessions

HideShow timer Statistics

A box has some red and some green balls in it. There are no balls of any other color. Some of these balls are heavy and the rest are all light. What is the probability that a heavy red ball is picked out of the box?

1. The probability of picking a heavy green ball is 20%
2. The probability of picking a light ball is 40%.

_________________

Resources
GMATNinja Webinars
GMATNinja Chats

Quant
Mixtures

Intern
Intern
avatar
B
Joined: 21 Nov 2016
Posts: 37
CAT Tests
Re: A box has some red and some green balls in it. There are no balls of  [#permalink]

Show Tags

New post 30 Sep 2018, 18:07
2
For the sake of convenience lets denote,
Light green = lg
Heavy green = hg
Light red = lr
Heavy red = hr
lg+hg+lr+hr = 100 % (say 100 balls)
Implies, lg+hg+lr+hr = 100

From statement 1 we have that the probability of picking up a hg is 20% . That is there are 20 balls which are heavy green out of those 100 balls.
Implies , hg+ lg+ lr+ hr = 100,
Implies, 20+ lg+ lr+ hr = 100,
Implies, lg + lr + hr = 80. But from this equation we do not know the value of heavy red ie hr.
So, insufficient.

Statement 2 says probability of picking a light ball is 40% that is there are 40 balls which are light out of those 100 balls.
So, hg + hr + lr + lg = 100
We have from statement 2, lg + lr = 40
So, hg + hr +40 = 100
Hg+ Hr = 60. Still we cannot find Hr.
So, Insufficient
.
From statement 1 we have , Hg = 20, so, substituting in the result of statement 2, we get , 20 + Hr = 60. Implies Hr = 40.
So the correct option is C.
Intern
Intern
avatar
B
Joined: 18 Mar 2018
Posts: 19
CAT Tests
A box has some red and some green balls in it. There are no balls of  [#permalink]

Show Tags

New post 10 Nov 2018, 06:21
This can be done by using a comparison table:

As no number has been assigned for the number of balls, pick a smart number of 100 for simplicity

-------R-----G------T
H-----x--------------
L---------------------
T------------------100

Statement 1: You have heavy and green balls, but no information on the number of light balls; NOT SUFFICIENT

-------R-----G------T
H-----x-----20---20+x
L---------------------
T------------------100

Statement 2: You can determine the total number of heavy balls from this but no information from the Green and Red split; NOT SUFFICIENT

-------R-----G-----T
H-----x-----60-x 60
L------------------40
T------------------100

Statement 1 & 2: Combining the 2, you have enough information by simply filling in the table

-------R-----G-----T
H-----x-----20---60
L------------------40
T------------------100

x = 60-20 = 40
Manager
Manager
avatar
B
Joined: 13 Nov 2018
Posts: 61
Location: India
GMAT 1: 700 Q51 V32
CAT Tests
Re: A box has some red and some green balls in it. There are no balls of  [#permalink]

Show Tags

New post 21 Nov 2018, 10:17
PeepalTree wrote:
A box has some red and some green balls in it. There are no balls of any other color. Some of these balls are heavy and the rest are all light. What is the probability that a heavy red ball is picked out of the box?

1. The probability of picking a heavy green ball is 20%
2. The probability of picking a light ball is 40%.


how c is correct and why not A

Prob(heavy green ball)=0.2

can we write

Prob(heavy red ball)=1-P(heavy green ball)

anyone can please explain simple way?
_________________

It seems Kudos button not working correctly with all my posts...

Please check if it is working with this post......

is it?....

Anyways...Thanks for trying :cool:

Intern
Intern
User avatar
B
Joined: 03 Sep 2018
Posts: 1
Location: India
Concentration: General Management
WE: Engineering (Energy and Utilities)
Re: A box has some red and some green balls in it. There are no balls of  [#permalink]

Show Tags

New post 21 Nov 2018, 19:41
gmatdordie

You missed out on including lighter balls

Prob(heavy red ball) + Prob(light red ball) + P(heavy green ball) + Prob(light green ball) = 1

Soln:

P(heavy green) = 1/5
P(light) = 2/5 => P(heavy) = 3/5

P(heavy green) = P(heavy) x P(green) [picking a ball based on weight and picking a ball based on color are mutually exclusive) => P(green) = 1/3 => P(red) = 2/3

P(heavy red) = P(heavy) x P(red) = 3/5 x 2/3 = 2/5

Bunuel can you crosscheck my reasoning. Thanks.
Intern
Intern
avatar
B
Joined: 26 Dec 2018
Posts: 25
Concentration: Finance, Economics
Re: A box has some red and some green balls in it. There are no balls of  [#permalink]

Show Tags

New post 17 Jan 2019, 13:48
1. P(HG)=.2
1-.2=.8=P(HR)+P(LR)+P(LG)

No way of determining probabilities of other marble groupings(insufficient).


2. 1-P(L)=.6=P(H)


On its own,insufficient.


1&2(combined).

P(HG)=P(H)*P(G)

.2=.6*P(G)


P(G)=.33

1-.33=.67=P(R)


P(R)*P(H)=P(HR)


.67*.6=.402 (sufficient
GMAT Club Bot
Re: A box has some red and some green balls in it. There are no balls of   [#permalink] 17 Jan 2019, 13:48
Display posts from previous: Sort by

A box has some red and some green balls in it. There are no balls of

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


Copyright

GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| GMAT Club Rules| Contact| Sitemap

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

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.