|
|
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
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
29 Jan 2018, 06:28
Kudos
Bookmarks
C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
25%
(medium)
Question Stats:
73% (01:24) correct
27%
(01:39)
wrong
based on 127
sessions
History
Date
Time
Result
Not Attempted Yet
A bag contains r red marbles, 5r + 4 white marbles and 3r + 2 blue marbles. If there are only red, white and blue marbles in the bag, what is the probability of pulling a red or white marble?
A. 1/9
B. 1/3
C. 2/3
D. 8/9
E. Cannot be determined.
A. 1/9
B. 1/3
C. 2/3
D. 8/9
E. Cannot be determined.
29 Jan 2018, 06:34
Kudos
Bookmarks
Bunuel
Since there are r red marbles, 5r+4 white marbles, and 3r+2 blue marbles,
there will be a total of 9r+6
Lets assume an arbitrary value for r=1. Now, there is 1 red marble, 9 white marbles, and 5 blue marbles.
Therefore, the probability of pulling a red or white marble in this case will be \(\frac{1+9}{1+9+5} = \frac{10}{15} = \frac{2}{3}\)(Option C)
Traditional Approach
Probability = \(\frac{P(Red,White)}{P(Total)} = \frac{r+5r+4}{9r+6} = \frac{6r+4}{9r+6} = \frac{2}{3}\)(Option C)
C
Total marbles = r + 5r + 4 + 3r + 2 = 9r+6.
Probability of getting red marbles = r/(9r+6)
Probability of getting white marbles = (5r+4)/(9r+6)
Hence, Probability of getting red or white marbles = r/(9r+6) + (5r+4)/(9r+6)
= (6r+4)/(9r+6)
= 2(3r+2)/(3(3r+2)
= 2/3
Total marbles = r + 5r + 4 + 3r + 2 = 9r+6.
Probability of getting red marbles = r/(9r+6)
Probability of getting white marbles = (5r+4)/(9r+6)
Hence, Probability of getting red or white marbles = r/(9r+6) + (5r+4)/(9r+6)
= (6r+4)/(9r+6)
= 2(3r+2)/(3(3r+2)
= 2/3
