Aptitude - Probability - Discussion
Discussion Forum : Probability - General Questions (Q.No. 12)
12.
A bag contains 4 white, 5 red and 6 blue balls. Three balls are drawn at random from the bag. The probability that all of them are red, is:
Answer: Option
Explanation:
Let S be the sample space.
| Then, n(S) | = number of ways of drawing 3 balls out of 15 | |||
| = 15C3 | ||||
|
||||
| = 455. |
Let E = event of getting all the 3 red balls.
 n(E) = 5C3 = 5C2 = |
(5 x 4) | = 10. |
| (2 x 1) |
| P(E) = |
n(E) | = | 10 | = | 2 | . |
| n(S) | 455 | 91 |
Discussion:
33 comments Page 4 of 4.
Naushad Farooqi said:
1 decade ago
For example: 5C3 = 5C2
5C3 = 5*4*3/3*2*1 = 5*4/2*1 (here 3 get cancelled)
5C2 = 5*4/2*1
Therefore, 5C3 = 5C2.
In 5C3, we can subtract 3 from 5 i.e. 5-3=2
So 5C3 will be equal to 5C2
There is question what is the use of it ?
to minimize the calculation .i.e. in case of 5C2 there are less calculation compare to 5C3.
Similarly: 6C4=6C2
Hope this will help you.
5C3 = 5*4*3/3*2*1 = 5*4/2*1 (here 3 get cancelled)
5C2 = 5*4/2*1
Therefore, 5C3 = 5C2.
In 5C3, we can subtract 3 from 5 i.e. 5-3=2
So 5C3 will be equal to 5C2
There is question what is the use of it ?
to minimize the calculation .i.e. in case of 5C2 there are less calculation compare to 5C3.
Similarly: 6C4=6C2
Hope this will help you.
Rohit jadhav said:
1 decade ago
Ya dinesh is right.
Dinesh guptha said:
1 decade ago
Don't confuse divya.
Keep it as 5C3.
You will get the same ans.
Cool!
Keep it as 5C3.
You will get the same ans.
Cool!
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