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  
= ^{15}C_{3}  


= 455. 
Let E = event of getting all the 3 red balls.
n(E) = ^{5}C_{3} = ^{5}C_{2} =  (5 x 4)  = 10. 
(2 x 1) 
P(E) =  n(E)  =  10  =  2  . 
n(S)  455  91 
Discussion:
32 comments Page 1 of 4.
Smrutiranjan Routray said:
10 months ago
Only red ball means;
5/15 * 4/14 * 3/13 = 60/2730 = 2/91.
5/15 * 4/14 * 3/13 = 60/2730 = 2/91.
(1)
Adnan Baig said:
11 months ago
Here it should be 5c3 becuase the selection of balls is 3 red balls.
(1)
SUDARSAN SWAIN said:
12 months ago
Why 5c2 is being calculated instead of 5c3? Please explain me.
(6)
Jino said:
3 years ago
@Deki Zangmo.
Thanks for the clear and best explanation.
Thanks for the clear and best explanation.
Poojitha said:
3 years ago
Total balls are 15.
Only we have to select red balls in total balls red are 5.
One selected from a total 5/13.
Next, another selected (we have already selected one so 1 ball is reduced from both red balls and total balls) == 4/14.
Here, 2 balls are reduced 1 from one selected ball another from again selected ball so 3/13
5/15 * 4/14* 3/13 = 2/91.
Only we have to select red balls in total balls red are 5.
One selected from a total 5/13.
Next, another selected (we have already selected one so 1 ball is reduced from both red balls and total balls) == 4/14.
Here, 2 balls are reduced 1 from one selected ball another from again selected ball so 3/13
5/15 * 4/14* 3/13 = 2/91.
(1)
Deki Zangmo said:
3 years ago
Total ball = 15.
Out of these, you have to select three balls.
15C3= 455,. We can select 3 balls in 455 ways.
But there is a condition that all 3 balls should be red so,
Out of 5 red balls we have to take out 3;
5C3 = 10,
As a result:
10/455 = 2/91.
Out of these, you have to select three balls.
15C3= 455,. We can select 3 balls in 455 ways.
But there is a condition that all 3 balls should be red so,
Out of 5 red balls we have to take out 3;
5C3 = 10,
As a result:
10/455 = 2/91.
(1)
Laxman said:
4 years ago
@USHA.
For example, there are 3 red balls and you have to select two balls out of it then possible ways are,
6 ways let me show;
R1,R2 R1,R3 R2,R1 R2,R3 R3,R1 R3,R1.
In these selections, we have R1, R2 and R2, R1 same like the way we consider only one so that we have 3 choices but don't consider you are selecting 3 out of 3 balls.
For example, there are 3 red balls and you have to select two balls out of it then possible ways are,
6 ways let me show;
R1,R2 R1,R3 R2,R1 R2,R3 R3,R1 R3,R1.
In these selections, we have R1, R2 and R2, R1 same like the way we consider only one so that we have 3 choices but don't consider you are selecting 3 out of 3 balls.
Pavanmahesh said:
4 years ago
All of them red balls means why it can be a 15c3?
Subash said:
5 years ago
Can any one explain clearly.
Sinchana said:
5 years ago
If the answer is 0.02 something how we can convert please explain it now.
(1)
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