(a) P(11,5)= 55440
(b) C(11,5)=462
We know that the permutation is the number of ways of arranging r items out of a total of n items and is given by:
[tex]P(n,r)=\dfrac{n!}{(n-r)!}[/tex]
and the combination is the number of ways of choosing r items out of a total of n items and is given by:
[tex]C(n,r)=\dfrac{n!}{r!\times (n-r)!}[/tex]
(a)
P(11,5)
[tex]P(11,5)=\dfrac{11!}{(11-5)!}\\\\P(11,5)=\dfrac{11!}{6!}\\\\P(11,5)=\dfrac{11\times 10\times 9\times 8\times 7\times 6!}{6!}\\\\P(11,5)=11\times 10\times 9\times 8\times 7\\\\P(11,5)=55440[/tex]
(b)
C(11,5)
[tex]C(11,5)=\dfrac{11!}{5!\times (11-5)!}\\\\C(11,5)=\dfrac{11!}{5!\times 6!}\\\\C(11,5)=\dfrac{11\times 10\times 9\times 8\times 7\times 6!}{5\times 4\times 3\times 2\times 1\times 6!}\\\\C(11,5)=462[/tex]