The factors of 2160 are 1, 2160, 2, 1080, 3, 720, 4, 540, 5, 432, 6, 360, 8, 270, 9, 240, 10, 216, 12, 180, 15, 154, 16, 135, 18, 120, 20, 108, 24, 90, 27, 80, 30, 72, 36, 60, 40, 54, 45, 48 These are all divisors of 2160 but only 30 are multiples of 3. The ones that are NOT are 1, 2, 4, 5, 8, 10, 16, 20, 40 and 80
You can also do this using prime factors 2x2x2x2x3x3x3x5 = 2160 but it is harder to explain.
Decision variables, as the name imply are entities that can have different values in the given scenario and which in turn produce different outcomes. For our question, the variables are the sizes of TVs available, as the production time and profit depend on the sizes. Hence, TV sizes (i.e. 5) are our decision variables.
Furthermore, it does not matter on which machine the TVs are being manufactured as they will take identical time for same TV size. Thus we do not consider the number of machines as our decision variables.
3/6 because there are 6 sides and there are 3 numbers that you want to roll. They are even numbers so if you want to roll half of the numbers but not the other half well you have 3/6