If you roll two number cubes, what is the probability of their sum being seven or higher?

1) Number of possible outcomes when 2 cubes are rolled = n^2 = 6^2 = 36
Possible outcomes for a sum = 7 are 6 as detailed below
(1,6) (2,5) (3,4) (4,3) (5,2) (6,1) = 6
Possible outcomes for a sum = 11 are 2 as detailed below
(5,6) (6,5) = 2
Required probability = 6/36 + 2/36 = 8/36 = 0.22222

2) Number of possible outcomes when a cube and a coin are tossed = m*n = 6*2 = 12
Possible outcomes for a tail and 6 = 1
Required probability = 1/12 = 0.08333

3) Possible outcomes for a sum =3 are 2 as detailed below
(1,2) (2,1) = 2
Possible outcomes for a sum = 8 are 5 as detailed below
(2,6) (3,5) (4,4) (5,3) (6,2) = 5
Required probability = 2/36 + 5/36 = 7/36 = 0.19444