Aptitude - Probability - Discussion

Discussion Forum : Probability - General Questions (Q.No. 10)

Probability

10.

Two dice are tossed. The probability that the total score is a prime number is:

Answer: Option

Explanation:

Clearly, n(S) = (6 x 6) = 36.

Let E = Event that the sum is a prime number.

Then E

= { (1, 1), (1, 2), (1, 4), (1, 6), (2, 1), (2, 3), (2, 5), (3, 2), (3, 4), (4, 1), (4, 3),
(5, 2), (5, 6), (6, 1), (6, 5) }

n(E) = 15.

P(E) =	n(E)	=	15	=	5	.
	n(S)		36		12

Discussion:

64 comments Page 4 of 7.

Ramya said: 1 decade ago

They have left out 6, 3 and 3, 6 then 5, 6 and 6, 5. These also should be included then the total probability becomes 1/2.

Sabin Basnet said: 3 years ago

When we add 1 and 1 it becomes 2.
So, 2 is not a prime number.
So, there is n(e) = 14 only
And 14/36 = 7/18.
That's all.

(3)

Prasad said: 1 decade ago

Hey why we cant take (1,3),(2,2,),(3,1)etc we can take others also na?

So please solve this in easy way.

Sweta said: 6 years ago

Are 4 and 6 prime numbers?

4 and 6 divisible by not only 1 and itself, but it is also divisible by 2, 3.

Kiran said: 9 years ago

You are considering (1, 1) is a prime set and why not you consider (2, 2), (3, 3), (5, 5) as a prime set?

NITIN RAJPUT said: 9 years ago

Thanks sir ,your are brilliant because you give me a platform to improve our objective paper skills..

Sirisha said: 7 years ago

1+1=2 here 2 is not a prime number then please explain why (1, 1) used here?

Explain, please.

Akshay said: 1 decade ago

Why don't we consider (1, 1) two times. Because it will be the outcome of both the dices.

Amit said: 1 decade ago

Why (1, 1) don't consider two times while sets like (1, 2) n (2, 1) is taken two times?

Sujit said: 1 decade ago

Don't you think we should not count (1,2) and (2,1) as 2 it must counted as 1 only.

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