Last visit was: 16 Jul 2024, 13:28 It is currently 16 Jul 2024, 13:28
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
SORT BY:
Date
Tags:
Show Tags
Hide Tags
Math Expert
Joined: 02 Sep 2009
Posts: 94370
Own Kudos [?]: 641408 [4]
Given Kudos: 85332
Send PM
GMAT Club Legend
GMAT Club Legend
Joined: 03 Oct 2013
Affiliations: CrackVerbal
Posts: 4918
Own Kudos [?]: 7802 [2]
Given Kudos: 220
Location: India
Send PM
Target Test Prep Representative
Joined: 14 Oct 2015
Status:Founder & CEO
Affiliations: Target Test Prep
Posts: 19148
Own Kudos [?]: 22647 [1]
Given Kudos: 286
Location: United States (CA)
Send PM
GMATWhiz Representative
Joined: 23 May 2022
Posts: 630
Own Kudos [?]: 475 [0]
Given Kudos: 6
Location: India
GMAT 1: 760 Q51 V40
Send PM
Re: If there are 30 red and blue marbles in a jar, and the ratio of red to [#permalink]
Expert Reply
Bunuel wrote:
If there are 30 red and blue marbles in a jar, and the ratio of red to blue marbles is 2:3, what is the probability that, drawing twice, the second marble is red, if you do not return the marbles after each draw?

A. 22/145
B. 1/25
C. 2/25
D. 2/5
E. 3/5


Solution:

  • Number of red balls \(=\frac{2}{2+3}\times 30=12\)
  • Number of blue marbles \(=\frac{3}{2+3}\times 30=18\)
  • Total cases of picking 2 marbles without replacing \(=30\times 29=870\)
  • Favorable case 1: 1st marble red and 2nd marble also red \(= 12\times 11=132\)
  • Favorable case 2: 1st marble blue and 2nd marble red \(=18\times 12=216\)
  • Required probability \(=\frac{Favorable case 1 + Favorable case 2}{Total cases} = \frac{132+216}{870}=\frac{348}{870}=\frac{2}{5}\)

Hence the right answer is Option D
User avatar
Non-Human User
Joined: 09 Sep 2013
Posts: 33994
Own Kudos [?]: 851 [0]
Given Kudos: 0
Send PM
Re: If there are 30 red and blue marbles in a jar, and the ratio of red to [#permalink]
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
GMAT Club Bot
Re: If there are 30 red and blue marbles in a jar, and the ratio of red to [#permalink]
Moderator:
Math Expert
94370 posts