In how many ways can 3 identical red balls, 3 identical green balls, and 3 identical blue balls be arranged in a 3x3 grid, such that each row and each column of the grid contains 1 ball of each color?
In first row, no. of color permutations = 3!
similarly for the next 2 rows = 2 * 6
Thus, total no. of ways are 12.