Answer:
15
Step-by-step explanation:
Given that:
Three six-sided dices are to be rolled.
The number of ways to have the same value on the two dices is:
{(1,1) ,(2,2) ,(3,3) ,(4,4) , (5, 5 ) ,(6 ,6) } = 6 ways
Thus; the objective is to determine the number of ways to a get smaller value on the third dice while the two other dice have the same value.
To get started:
The number of ways for getting a value smaller than 1 = 0
The number of ways for getting a value smaller than 2 = 1
{i.e. (2,2,1)}
The number of ways for getting a value smaller than 3 = 2
{ i.e. (3,3,1) ,(3,3,2) }
The number of ways for getting a value smaller than 4 = 3
{ i.e. (4,4,1) , (4,4,2), (4,4,3)}
The number of ways for getting a value smaller than 5 = 4
{i.e. (5 ,5,1) ,(5,5,2) ,(5,5,3), (5,5,4)}
The number of ways for getting a value smaller than 6 = 5
{i.e. (6,6,1), (6,6,2), (6,6,3), (6,6,4), (6,6,5) }
Thus, the total number of ways = 0 + 1 + 2 + 3 + 4 + 5 = 15
Therefore, the total number of ways getting the value same on two dices and smaller value on the third dice = 15
