An election ballot asks voters to select four city commissioners from a group of sixteen candidates. In how many ways can this be done?

Answer: 1820

Step-by-step explanation:

The first can be selected in 16 ways, the second in 15 ways, the third in 14 ways and the last in 13 ways

i. e. 16 x 15 x 14 x 13 = > 43680

However, the order of the candidates does not matter and they can be selected in 4 x 3 x 2 x 1 = > 24 ways

so, 43680/24 = > 1820