Question 1166681
Let A be the sum is odd
Let B be the sum is a multiple of three

P(A or B)=P(A)+P(B)-P(A and B)

Possible odd sums: 3,5,7,9,11

3: (1,2) or (2,1)
5: (1,4), (4,1), (3,2), or (2,3)
7: (2,5), (5,2), (3,4), (4,3), (6,1), or (1,6)
9: (3,6), (6,3), (5,4), or (4,5)
11: (5,6),(6,5)

This could occur 18 times out of 36 dice roll possibilities.

So, P(A) = {{{1/2}}} or 0.5 or 50% 

Possible multiples of 3:

3: (1,2) or (2,1)
6: (1,5), (5,1), (2,4), (4,2), (3,3)
9: (3,6), (6,3), (5,4), or (4,5)
12: (6,6)

This could occur 12 times out of 36 dice roll possibilities.

So, P(B) = {{{1/3}}} or 0.33 or 33%

Now, we need to find the possibilities they have in common. They are:

3: (1,2) or (2,1)
9: (3,6), (6,3), (5,4), or (4,5)

This could occur 6 times out of 36 dice roll possibilities.

So, P(A and B) = {{{1/6}}} or 0.166 or 16.6%

Since P(A or B)=P(A)+P(B)-P(A and B):

P(A or B) = {{{1/2}}}+{{{1/3}}}-{{{1/6}}}={{{2/3}}}

Rounded to the nearest tenth of a percent: P(A or B) = 66.7%