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 7 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.
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?
Anil pradhan said:
1 decade ago
Simple and clear way is:
Probability of getting blue is 2/7.
And getting non-blue is 1-2/7 = 5/7.
i.e Total probability-Probability of blue ball.
Probability of getting blue is 2/7.
And getting non-blue is 1-2/7 = 5/7.
i.e Total probability-Probability of blue ball.
Prabhat kumar mishra said:
1 decade ago
Total number of balls = 7.
Therefore first probability is = 5/7and second probability will be 4/6.
Hence, total probability = (5/7)*(4/6) = 20/42 = 10/21.
Therefore first probability is = 5/7and second probability will be 4/6.
Hence, total probability = (5/7)*(4/6) = 20/42 = 10/21.
ARUN KASHYAP said:
1 decade ago
Answer is simple:
2+3+2 = 7x3(here 3 is no.of 2+3+2) = 21.
2+ 3(here 3 is no.of 2+3+2) = 5x2 = 10.
10/21.
2+3+2 = 7x3(here 3 is no.of 2+3+2) = 21.
2+ 3(here 3 is no.of 2+3+2) = 5x2 = 10.
10/21.
Mohammad Javed said:
1 decade ago
There is one easy way.
No balls should be blue means either it should be red or green which sums to 5 balls. Total balls is 7.
Probability of no blue will be = (5/7)*(4/6)=10/21.
As we have picked one ball we are reducing Red+Green balls to 4. And total balls to 6.
No balls should be blue means either it should be red or green which sums to 5 balls. Total balls is 7.
Probability of no blue will be = (5/7)*(4/6)=10/21.
As we have picked one ball we are reducing Red+Green balls to 4. And total balls to 6.
Stephen said:
1 decade ago
Is there an easier way of doing these type of probability word problems?
Chandani said:
1 decade ago
Please answer this question. What is the number of ways of selecting 3 balls from a bag containing 5 blue and 6 red balls. If the answer is 11C3 please explain what about the cases where 2 are blue and 1 red.
This will happen a number of times, but they will all be counted as separate selections. How do we account for the similarity. Please help.
This will happen a number of times, but they will all be counted as separate selections. How do we account for the similarity. Please help.
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