It is currently 28 Jun 2017, 21:30

### 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

# John must select a marble from a bag containing red,green

Author Message
Director
Joined: 25 Oct 2008
Posts: 596
Location: Kolkata,India
John must select a marble from a bag containing red,green [#permalink]

### Show Tags

25 Jul 2009, 03:51
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 100% (00:58) wrong based on 1 sessions

### HideShow timer Statistics

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

John must select a marble from a bag containing red,green and blue marbles.If there are 20 marbles or fewer in the bag,is the probability that he will select a red marble greater than 1/4?
1.there are twice asmany blue marbles as green marbles
2.There is a 3/5 probability that the marble chosen will not be blue.
_________________

http://gmatclub.com/forum/countdown-beginshas-ended-85483-40.html#p649902

CEO
Joined: 17 Nov 2007
Posts: 3584
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Re: probability that he will select a red marble greater [#permalink]

### Show Tags

27 Jul 2009, 08:11
C

1) it is insufficient. For (4 blue, 2 green, and 1 red) the probability is 1/7 < 1/4 but for (4 blue, 2 green, and 6 red) the probability is 1/2 > 1/4.

2) In other words, the probability of getting blue marble is 1-3/5 = 2/5. The probability of getting red could range from 1/20 (1 red marble from 20 marbles) to 11/20. Insufficient.

1)&2) 2/5 for blue, 1/5 for green and 1-2/5-1/5 = 1/5 for red. Sufficient.

I don't know why we need <=20 marbles here. Maybe I missed something....
_________________

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

Manager
Joined: 21 Jun 2009
Posts: 154
Re: probability that he will select a red marble greater [#permalink]

### Show Tags

27 Jul 2009, 10:47
1 and 2 are insufficient for the resons cited above.
1+2) Probability of getting a blue marble = 2/5
From 1) There are twice the number of blue marble as green marble,
probabiliyt of getting a green marble = (1/5) - has to be half

Probability of picking a red marble = 1 - (2/5)+ (1/5) = 1- (3/5) = 2/5 which is > 1/4 - no need to solve it but we know that this is sufficient.
Manager
Joined: 05 Jul 2009
Posts: 181
Re: probability that he will select a red marble greater [#permalink]

### Show Tags

27 Jul 2009, 23:56
So the mention of numbers is only to deceive...
Re: probability that he will select a red marble greater   [#permalink] 27 Jul 2009, 23:56
Display posts from previous: Sort by