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May 6th, 2015, 06:23 AM   #1
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Question Arrangement problems

The prime minister A,B,C,D,E,F and G of 7 countries will address at a summit meeting.

(a) Find the number of arrangements that can be made so that

(i) A will speak before C
(ii) A will speak before C and C before E

(b) In how many of those ways in (a ii) will C speak immediately after A ?

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May 6th, 2015, 07:20 AM   #2
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(a i) $\displaystyle \binom{7}{2}\cdot 5!$

(a ii) $\displaystyle \binom{7}{3}\cdot 4!$
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May 6th, 2015, 09:41 AM   #3
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Hello, new hand!

Quote:
The prime ministers of 7 countries {A,B,C,D,E,F,G}
will address at a summit meeting.

(a) Find the number of arrangements that can be made so that
(i) A will speak before C

There are possible arrangements.

In half of them, A will precede C.




Quote:
(ii) A will speak before C and C before E.

I'm getting two different answers.
I'll have to work on it . . .




Quote:
(b) In how many of those ways in (a ii)
will C speak immediately after A?



There are: arrangements.

In half of them, will precede


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May 8th, 2015, 12:29 PM   #4
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Hello, new hand!

Quote:
The prime ministers of 7 countries {A,B,C,D,E,F,G}
will address at a summit meeting.

(a) Find the number of arrangements that can be made so that
(ii) A will speak before C and C before E.









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