Problem Solving

Thanks in advance

nahid078 wrote:Thanks in advance

Tricky question. First, the possible prime numbers that can be sum of two dices are 2, 3, 5, 7, and 11.

Next, note that there are 6 x 6 = 36 possible ways the two dices can come up.

Of the 36 different combinations:

1 can sum to 2 (both dices are 1s)
2 can sum to 3 (2,1 or 1,2)
4 can sum to 5 (1,4; 4,1; 3,2; or 2,3)
6 can sum to 7 (1,6; 6,1; 2,5; 5,2; 4,3; or 3,4)
2 can sum to 11 (5,6 or 6,5)

Therefore, the total number of possible outcomes in which the sum of the two dices is a prime number is 15.

The probability is thus 15/36, which reduces to 5/12. Choice A