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kevincan
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is it \(6*6* 5!\)

There are 6 possible ways to arrange two consecutive concerts in a city and remaining 5 can be arranged in 5 cities 5! ways. Also we can pick city for double concert in 6 ways.
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A folk group wants to have one concert on each of the seven consecutive nights starting January 1 of next year. One concert will be held in each of cities A, B, C, D and E, and two will be held in city F, one of each of two non-consecutive nights. In how many ways can the group decide on the venues for these seven concerts?

Sorry, no choices! Let's see what we come up with...

The wording is a bit confusing at the red part.
Here is my shot at it:
A, B, C, D, E, F, F => Total 8!
Can't have (F,F) together, and the total combination of that is:
A, B, C, D, E, (F, F) => Total 6!
Ans = 8! - 6!

Why you did 8! and 6! instead of 7! and 5!?

the red part means, imo, 2 concerts cannot be happen consecutively in city F. suppose if one concert held on 1 then next can be on either of 3 or 4 or 5 or 6 or 7 and so on.

so total possibilities = 7!
consecutive concerts in city F = 2 (5!)
so no of ways the concert can be held = 7!- 2 (5!)

Yea, it should be 7! for the total, I think I was dreaming.
I think it should be 7! - 6! though, two concerts in F doesn't differentiate which comes first.
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So when are we to get OA and OE on this.

Looks like bkk* answer matches with what I have got with different way...want to make sure my approach is right.

7!-6!= 6!*(7-1) = 6!*6 = 6*6*5!
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Step One: Decide which two non-consecutive concerts will be be held in F: 7C2 - 6 = 15
Step Two: Assign venues A, B, C, D and E to the remaining 5 concerts: 5! = 120

Answer: 15 x 120= 1800
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Kevincan

I had 6*6*120

I see that I made a mistake assuming any of the cities is valid for double concert, for that I can reduce my answer to

6*120

I dont get your calculation on \(7C2-6\)
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kevincan
Step One: Decide which two non-consecutive concerts will be be held in F: 7C2 - 6 = 15
Step Two: Assign venues A, B, C, D and E to the remaining 5 concerts: 5! = 120

Answer: 15 x 120= 1800

did not get what you did! :roll:
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kevincan
Step One: Decide which two non-consecutive concerts will be be held in F: 7C2 - 6 = 15
Step Two: Assign venues A, B, C, D and E to the remaining 5 concerts: 5! = 120

Answer: 15 x 120= 1800

Clarifying Step One: Of the seven days, choose two on which a concert will be held in F. There are 7C2 =7!/5!2! ways of doing so, but we must eliminate the 6 ways in which two consecutive days are chosen
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kevincan
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Step One: Decide which two non-consecutive concerts will be be held in F: 7C2 - 6 = 15
Step Two: Assign venues A, B, C, D and E to the remaining 5 concerts: 5! = 120

Answer: 15 x 120= 1800

Clarifying Step One: Of the seven days, choose two on which a concert will be held in F. There are 7C2 =7!/5!2! ways of doing so, but we must eliminate the 6 ways in which two consecutive days are chosen


Based on how I interpreted it , I thought whats required is opposite of above bold-underlined statemant you made....its 6ways we can choose a city as concert in city F has 2 back to back events.

Not sure what I am missing.
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The question specifies that the two concerts in F must not be on consecutive nights
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I am not good for GMAT. I cant even read question well. :cry:
No point knowing all the math behind if question is not read properly. Lesson learnt, again!

With this rather important correction :P I agree with your answer.
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Here's my shot at it:

F 5 4 3 2 1 F= 120 ways
F 5 4 3 2 F 1= 120 ways *2 (Since it is symmetric to _ F _ _ _ _ F)
F 5 4 3 F 2 1 = 120 ways * 2 (symmetric to _ _ F _ __ F)

These are the nly ways, and I am gettinn the ans to be 600.

Does anyone have the OA/OE?
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OA and OE

Quote:
Step One: Decide which two non-consecutive concerts will be be held in F: 7C2 - 6 = 15
Step Two: Assign venues A, B, C, D and E to the remaining 5 concerts: 5! = 120

Answer: 15 x 120= 1800



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