App description

<div align=left> <img src="/static/upload/f1/f12e7856-b8e9-11ea-a97b-00163e0618d6_m.jpg" style="width:50%"/> </div>

Usage example

Arrange the calculator for P(n,r) Input data: input n = 7; input r = 4

<div align=left> <img src="/static/upload/05/05b9ff8e-b8ea-11ea-8d75-00163e0618d6_m.jpg" style="width:50%"/> </div>

Note

Symbol description: P-permutation number (now textbook A), total number of n-elements, number of r-elements involved in selection,!-factorial,as 5！=5 * 4 * 3 * 2 * 1=120 C-Combination combination P-Permutation array (Now the textbook is A-Arrangement)