Question

In a single throw of a pair of different dice, what is the probability of getting (i) a prime
number on each dice? (ii) a total of 9 or 11?

Answer 1

p of getting a prime no on each dice is 3/36=1/12
p of getting a total of 9 or 11 is 6/36=1/6

Answer 2

(i) Favourable outcomes are (2, 2) (2, 3) (2, 5) (3, 2)   (3, 3) (3, 5) (5, 2) (5, 3) (5, 5) = 9 outcomes

P (a prime number on each die) = $\bf\huge\frac{9}{36}$

=  $\bf\huge\frac{1}{4}$

(ii) Favourable outcomes are (3, 6) (4, 5) (5, 4)  (6, 3) (5, 6) (6, 5) i.e. 6 outcomes

P (a total of 9 or 11) = $\bf\huge\frac{6}{36}$

= $\bf\huge\frac{1}{6}$