Answer:
116,280 ways
Step-by-step explanation:
Because your finish place is mutually exclusive (if you come in first you cant come in second, if you come in second you cant come in third, etc) you have to decrease the amount of runners for each place.
20 runners can get first
19 for second
18 for third
17 for fourth.
To find out the total amount of possibilities you multiply each amount. 20 x 19 x 18 x 17 = 116,280.
I hope this helps!
-TheBusinessMan
