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 1 of 4.

Chris said:   2 years ago
@All.

Here, You can solve it in two ways.

Method 1:
Total number of balls = 7+8+6= 21.
Neither red nor green, that means it is blue,
Number of blue = 7,
Probability of blue = number of blue balls÷ total number of balls.

Probability of blue balls= 7/ 21.

1/3.

Method 2:
Total number of balls = 21.
Number of Red = 8.
Prob of selecting red = 8/21 or.
Number of Green = 6.
Prob of selecting green = 6/21 or 2/7.
Neither Red nor Green = 1-(prob of red+ prob of green).
1 - (8/21 + 6/21).
1 - 14/21 = 7/21 or 1/3.
(10)

Kigele yazidi said:   1 year ago
Total number of balls = 8 + 7 + 6,
=21.

Probability not red or green= number of events/sample space.
So, 7÷21 = 1/3.
(3)

Boopathy said:   7 years ago
Probability of selection Red or Green= 8+6=14 / 21 = 2/3.

Then how 1/3?
(1)

Tushar dhok said:   7 years ago
Total no.of ball 8, 7, 6 = 21.

E= event that the ball is neither red nor green.
= event that the ball is red.
n(E) = 8.
P(E) = 8/21.
(1)

Anitha said:   7 years ago
How it is possible?
(1)

Ravindra said:   5 years ago
How can p(e) =7?

Because neither red nor green clearly means its blue.
(1)

Romeo said:   2 years ago
Thanks all for explaining.
(1)

Rohit said:   5 years ago
How n(E) =7?

Anitha said:   6 years ago
Total no.of balls =8+7+6=21,
Neither red nor green,
I.e.,we need to take 8,
Therefore p(e)=8/21.

Tharunteja said:   6 years ago
Guys it may be a wrong answer.

The actual correct answer;

Total no.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 (given neither red nor green) make a note this point.
therefore p(E) = 8/21.


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