Plz
 

hello everybody... this is my first time in this forum, well i have this problem, can anyone kindly help me in solving it:
a police station will start making a night shift, and there are 20 policemen.

a.if a night team includes 3 policemen, how many different teams are possible to have??

b.if the policemen are ranked 1,2,...,20 in order of doing well, how many of these teams will not have the beat policemen??

c.How many the teams will have at least 1 of the best 10 policemen??

d.if one of these teams is selected at random to work in a particular night, what is the possibliy that the best policeman will not work that night??

Re: Plz
 

[ QUOTE ]
a.if a night team includes 3 policemen, how many different teams are possible to have??

[/ QUOTE ]
C(20,3) = 1140


[ QUOTE ]
b.if the policemen are ranked 1,2,...,20 in order of doing well, how many of these teams will not have the beat policemen??

[/ QUOTE ]
C(19,3) = 969

[ QUOTE ]
c.How many the teams will have at least 1 of the best 10 policemen??

[/ QUOTE ]
C(20,3) - C(10,3) = 1020

[ QUOTE ]
d.if one of these teams is selected at random to work in a particular night, what is the possibliy that the best policeman will not work that night??

[/ QUOTE ]

I'm not exactly sure what you're getting at with this. Is this assuming they were divided up into 7 teams (6 teams of 3 and 1 team of 2), or out of the 1140 possible teams?

I'll assume 1140 possible teams:
C(19,3)/C(20,3) = 85%, or just the obvious 17/20.

Re: Plz
 

Maybe "she's" trying to figure out which corner to work?

[img]/images/graemlins/blush.gif[/img]

Re: Plz
 

If you get internet forums to do your homework, the bad beat policemen will come and get you, you know that?

Say goodbye to ever winning with Aces again...