We have been given two expressions . We are asked to find the value of each.
To find 9P9, we will use permutations formula.
, where
P = Number of permutations,
n = The total number of objects in the set,
r = Number of objects being chosen from the set.
Using
To find 9C9, we will use combinations formula.
, where
C = Number of combinations,
n = The total number of objects in the set,
r = Number of objects being chosen from the set.
Using
Cancelling out , we will get:
The answers differ because order. With permutations we care about the order of the elements, while with combinations we don't.