Aptitude - Probability - Discussion

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.

@Harshini.

Permutations are used for arrangement where as combinations are used for selection.

Ex: Arrange the name xyz then per is used.

Where as,

Select one among this xyz comb is used.

Prime number means the we gets only one time. i.e., 1*2=2 only once we get 2. But for 4 1*4=4, 2*2=4 now we get 4 for 2 times in-terms of multiplication.

Please in every example we need to find samples or experiment samples or there is any shortcut for easily getting number of prime number or sum of two numbers as a prime ?

As the question says sum should be a prime number.

So sum must be 2, 3, 5, 7, 11,

So probability should be (1, 1) (1, 2) (2, 1) (1, 4) (4, 1) (3, 4) (4, 3) (5, 6) (6, 5).

So probability= (9/36) =1/4.

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

The sample space is a set, so repeated event (1, 1) is taken only once.

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

Finally I found the answer of this question. It is very simple.

When two dice are tossed the total number of possibilities are 36.

Which means 6*6 =36. They are asked to find out the prime number. We know what is prime number, the number is divisible by the same number except 1.

In this concept the possibilities are
(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).

from {(1,1), (1,2)... (6,6)}.

1+1=2, 1+2=3, 1+4=5, 1+6=7 the same way you can get the indivisible numbers expect the same number. So answer is 15/36 which is equal to 5/12 is the correct answer :-).

Hey if you take 5, 6 and 6, 5 as a different pair then why you don't take (1, 1) and (1, 1) as different pairs because it is first time 1 and second time 1.