Question

Two fair number cubes are rolled. What is the probability the numbers are equal or the sum is odd?

Answer 1

0.6667 = 66.67%

Explanation:

If each number cube has 6 numbers, the two cubes have a total of 6 * 6 = 36 results.

To have equal numbers in each cube, the cases are:

(1,1), (2,2), (3,3), (4,4), (5,5), (6,6) -> 6 cases

To have a odd sum, the cases are:

(1,2), (1,4), (1,6),

(2,1), (2,3), (2,5),

(3,2), (3,4), (3,6),

(4,1), (4,3), (4,5),

(5,2), (5,4), (5,6),

(6,1), (6,3), (6,5). -> 18 cases

So we have a total of 18 + 6 = 24 cases, then the probability is:

P = 24 / 36 = 0.6667 = 66.67%