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

27 rolls of being 7 or higher