# Aptitude - Probability - Discussion

Discussion Forum : Probability - General Questions (Q.No. 3)
3.
In a box, there are 8 red, 7 blue and 6 green balls. One ball is picked up randomly. What is the probability that it is neither red nor green?
 1 3
 3 4
 7 19
 8 21
 9 21
Answer: Option
Explanation:

Total number of balls = (8 + 7 + 6) = 21.

 Let E = event that the ball drawn is neither red nor green = event that the ball drawn is blue.

n(E) = 7.

 P(E) = n(E) = 7 = 1 . n(S) 21 3

Discussion:
36 comments Page 3 of 4.

Mangesh Modiraj said:   1 decade ago
@Nandini & @Monica.

In example clearly mentioned that the ball ins neither red nor green.

i.e blue.

We have 7 blue balls.

Therefore n(E) = 7.

Muhammad Imran Tariq said:   1 decade ago
Sample= 8+7+6=21.

Probability of selection Red and Green= 8+6=14 / 21 = 2/3.

Not selection of Red and Green. Simple subtracts 1 from 2/3.

1 - 2/3= 1/3 (Answer).

Farah said:   1 decade ago
Please all students read question carefully what he ask in question. He said that 8 red, 6 green, 7 blue total=21 probability ?

He said neither from red and green so only one option is 7 blue.

7c1 which is n(a)=7 and n(S)=21c1=21

Formula is prob. p(A)=n(A)/n(S)

7/21 = 1/3.

Angamuthu SURESH said:   1 decade ago
Total number of balls = (8 + 7 + 6)
= 21.
Let E = event that the ball drawn is neither red nor green
=event that the ball drawn is red.
Therefore, n(E) = 8.
P(E) = 8/21.

Hina said:   1 decade ago
What is the meaning that die is fair or not?

Sree said:   1 decade ago
There is a die with 10 faces. It is not known that fair or not. 2 captains want to toss die for batting selection. What is the possible solution among the following?
a) If no. is odd it is head, if no. is even it is tail
b) If no. is odd it is tail, if no. is even it is head
c) Toss a die until all the 10 digits appear on top face. And if first no. in the sequence is odd then consider it as tail. If it is even consider it as head.
what is the exact solution

S.Ranga reddy said:   1 decade ago
Hear there are 1 randomly selected means
green 8 blue 6
average of 2colors
so 8+6=14
14/2=7

Sahi said:   1 decade ago
Hi aruna I think you didn't read the question properly it is clearly mentioned that neither red nor green, so the remaining are blue. Hence we hve to consider blue balls. Hope you got it :).

Aruna said:   1 decade ago
Neither red nor blue.

Then why we are take 7 blue balls only.

Can't understand.

Please clear my doubt.

Sravani said:   1 decade ago
n(E) =7 because there are 7 blue balls.

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