Question

When rolling two die, what is the probability of one die being even or the sum is 5

Answer 1

Solution:

number of total possibilities when rolling two dies = 6 * 6 = 36

number of possibilities of one die is even = 2 * 3 * 3 = 18

( explanation: first, place 3 even numbers in one of the dies and then place 3 odd numbers on the remaining die . so, the number of possibilities are 3*3 = 9 ,and then place 3 even numbers on the other die and place 3 odd number on the remaining die .so, the number of possibilities are 3 * 3 = 9 . total number of possibilities of one die being even = 9 + 9 = 18 )

possibilities of sum being 5 are : (1,4)(2,3)(3,2)(4,1)

number of possibilities of sum being 5 = 4

among these all possibilities are only one die being even . so,

the probability of one die being even or the sum is 5 = ( 18 - 0 )/ 36 = 0.5