Question

Quantos números de 3 algarismos distintos que podemos formar com os algarismos 1,2,3,4,5,6 e 7 ?

Answer 1

$A_{n,p}=\frac{n!}{(n-p)!}\\\\A_{7,3}=\frac{7!}{4!}\\\\A_{7,3}=\frac{7\cdot6\cdot5\cdot4!}{4!}\\\\A_{7,3}=7\cdot6\cdot5\\\\\boxed{A_{7,3}=210}$