Question

What are ${}^{n}P_r$ and ${}^{n}C_r$ in math?

Answer 1

${}^{n}P_r$:

• ${}^{n}P_r$ represent the permutation.
• The permutation is the arrangement of the items into some sequence or order.
• The number of ways of arranging $r$ items from a set of $n$ items is: ${}^{n}P_r=\frac{n!}{\left(n-r\right)!}$

${}^{n}C_r$:

• ${}^{n}C_r$ represent the combination.
• The combination is the selection of the items where the order of the items does not matter.
• The number of ways of selecting $r$ items from a set of $n$ items is: ${}^{n}C_r=\frac{n!}{r!\left(n-r\right)!}$