Aptitude - Probability - Discussion
Discussion Forum : Probability - General Questions (Q.No. 2)
2.
A bag contains 2 red, 3 green and 2 blue balls. Two balls are drawn at random. What is the probability that none of the balls drawn is blue?
Answer: Option
Explanation:
Total number of balls = (2 + 3 + 2) = 7.
Let S be the sample space.
| Then, n(S) | = Number of ways of drawing 2 balls out of 7 | |||
| = 7C2 ` | ||||
|
||||
| = 21. |
Let E = Event of drawing 2 balls, none of which is blue.
 n(E) |
= Number of ways of drawing 2 balls out of (2 + 3) balls. | |||
| = 5C2 | ||||
|
||||
| = 10. |
| P(E) = |
n(E) | = | 10 | . |
| n(S) | 21 |
Discussion:
117 comments Page 9 of 12.
Sarah said:
1 decade ago
The formula for ncr = n!/(n-r)!*r! if you submit values in this you can get the answer.
John said:
1 decade ago
Probability of occurrence of blue ball.
1 blue AND 1 blue OR,
1 red/green AND 1 blue OR,
1 blue AND 1 red/green.
(2/7 * 1/6) + (5/7 * 2/6) + (2/7 * 5/6) = 11/21.
Probability of non-occurrence of blue ball = 1-(11/21) = (10/21) ANS.
1 blue AND 1 blue OR,
1 red/green AND 1 blue OR,
1 blue AND 1 red/green.
(2/7 * 1/6) + (5/7 * 2/6) + (2/7 * 5/6) = 11/21.
Probability of non-occurrence of blue ball = 1-(11/21) = (10/21) ANS.
Hari said:
1 decade ago
Supriya c2 means multiply with number below it. Suppose 2c2= 2*1.
Bhavna said:
1 decade ago
I didn't understand the method which sagar did? can anybody make it clear!
Sundry said:
1 decade ago
From the explanation, where did 6 come from? why did you multiply 7 by 6? I did not understand that one.
Zuay said:
1 decade ago
No no no! I don't understand are we not suppose to consider probability of not obtaining blue balls here? then its 5/7.
Supriya said:
1 decade ago
How the (7*6)(2*1) has come?
Please clear my concept.
Please clear my concept.
PRASHANT SINHA said:
1 decade ago
In the same question what is the probability of taking 2 blue balls?
Manjunath said:
1 decade ago
In the same question what is the probability of taking 2 blue balls?
Navcool said:
1 decade ago
Is it with or without replacement?
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers