Consider <u>6 potted plants</u> that you are going to <u>arrange in a row</u>. You can choose first plant in 6 ways (one plant from 6 given), then 5 plants left to be arranged. The second plant can be chosen in 5 ways (one plant from remaining 5) and after you arrange the second plant, only 4 plants left. The third plant you can choose in 4 ways (one plant from remaining 4) and after this procedure only 3 plants left. The fourth plant you can choose in 3 ways (one plant from remaining 3) and only 2 plants left. The fifth plant you can choose in two ways and the last one is determined by the 5 previous.
Then the number of ways to arrange 6 potted plants in a row is