Chapter 11 - Probability and Statistics - 11-1 Permutations and Combinations - Practice and Problem-Solving Exercises - Page 678: 21

$8$

Use the formula $P(n,r)=\dfrac{n!}{(n-r)!}$. We have $n=8$ iand $r=1$: Substitute these values into the formula above to obtain: $P(8,1)=\dfrac{8!}{(8-1)!}\\$ $P(8,1)=\dfrac{8!}{7!}\\$ $P(8,1)=\dfrac{8*7*6*5*4*3*2*1}{7*6*5*4*3*2*1}$ Cancel out common numbers to get: $P(8, 1)= 8$