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.
Shashikant sahu said:
7 years ago
This is a very simple technique.
1st ball not to be blue is = (1-2/7)=5/7.
Now next ball not to be blue is = (1-2/6)=4/6.
*(causes 1 ball has already taken).
Multiple both;
= 5/7 * 4/6.
= 10/21.
1st ball not to be blue is = (1-2/7)=5/7.
Now next ball not to be blue is = (1-2/6)=4/6.
*(causes 1 ball has already taken).
Multiple both;
= 5/7 * 4/6.
= 10/21.
Ritu verma said:
7 years ago
Prob of 1st ball not blue * prob of 2nd ball not blue.
= (5/7)*(4/6),
= 20/42,
= 10/21.
= (5/7)*(4/6),
= 20/42,
= 10/21.
Ahmed said:
7 years ago
Simply, find the probability of getting 2 balls blue then subtract from 1.
Trini said:
7 years ago
7c2 -> 7!/(7-2)! 2! which is 7*6*5!/5!2! = 7*6/2*1 = 21.
Pragya said:
7 years ago
C2 stands for what? Please explain me.
Tenzin said:
7 years ago
It's answers is 5/7.
1 1,1 2,2 1,3 1,3 2,
Five ways that we get the ball without getting a blue ball,
So it should be 5/7.
1 1,1 2,2 1,3 1,3 2,
Five ways that we get the ball without getting a blue ball,
So it should be 5/7.
Aman said:
8 years ago
@Jaani.
What is the probability of picking 2 blue ball then what is the probability?
What is the probability of picking 2 blue ball then what is the probability?
Suyash said:
8 years ago
Simply, say 5/7 * 4/6.
= 10/21.
= 10/21.
Bikash said:
8 years ago
Can you please explain in detail what is mean by C and all?
Deepali said:
8 years ago
I understand the explained method but 7C2 means factorial of 7 so there should be 7*6*5*4*3*2*1/2*1. Wwhy in explanation they took only 7*6. Please explain it.
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