NIMCET 2013 Question Paper with solutions

Question : 43 of 120

Marks: +1, -0

Two fair dice are tossed. What is the probability that the total score is a prime number ?

16
5/12
1/2
7/9

Solution:

Sum is a prime number i.e. the sum of the dice outcomes can be 2, 3,5,7,11.
These sums are shown in following pairs
(1,1), (1,2), (2, 3), (3, 4), (5, 6)
(5, 2), (4,1), (2,1), (4, 3), (6, 5)
(2, 5), (1,4), (3, 2), (1,6), (6,1)
∴ Required probability

=15/36=5/12

[2 dice

=6×6=36

]

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