Question

If you look at the following k-map, you should notice that only two of the input variables- A, B, C, D change their state, in the marked group. The other two variables hold the same value '1'. Identify which variable change, and which stay the same:

Answer 1

In a K-map group, the variables that change between 0 and 1 are eliminated from the product term. The two variables that remain constant at 1 are retained as uncomplemented literals. Thus, read the row and column labels of the marked group: the changing variables are omitted, while the two fixed variables remain as their product.