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:
116 comments Page 4 of 12.
Supriya said:
1 decade ago
How the (7*6)(2*1) has come?
Please clear my concept.
Please clear my concept.
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.
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.
Bhavna said:
1 decade ago
I didn't understand the method which sagar did? can anybody make it clear!
Hari said:
1 decade ago
Supriya c2 means multiply with number below it. Suppose 2c2= 2*1.
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.
Sarah said:
1 decade ago
The formula for ncr = n!/(n-r)!*r! if you submit values in this you can get the answer.
Chi said:
1 decade ago
What is the formula for this question?
Nagen said:
1 decade ago
Whether sum of probability of 1 blue plus 2 blue is not opposite of none blue.
Shivam said:
1 decade ago
Why are we taking combination and not permutation in this question?
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