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birthday for dinner

by sanju09 » Wed Jan 27, 2010 12:02 am
A man has to invite six of his friends on his birthday for dinner. He can send invitations by post, by phone, or by his servant. In how many ways can he send invitations to his friends so that each of his friends gets only one invitation?
(A) 120
(B) 216
(C) 360
(D) 720
(E) 729
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by ajith » Wed Jan 27, 2010 12:27 am
sanju09 wrote:A man has to invite six of his friends on his birthday for dinner. He can send invitations by post, by phone, or by his servant. In how many ways can he send invitations to his friends so that each of his friends gets only one invitation?
(A) 120
(B) 216
(C) 360
(D) 720
(E) 729
Each of the 6 friends can be invited in 3 ways, total number of ways = 3^6 = 729
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by thephoenix » Wed Jan 27, 2010 1:11 am
each person has 3 option
3*3*3*3*3*3=3^6=729
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by hai1 » Wed Jan 27, 2010 1:52 am
As the invitation can go only once, hence this is a permutation without repetetion.

My answer is: 6X5X4=120.

I am no expert, but this is just my answer!
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by ajith » Wed Jan 27, 2010 1:57 am
hai1 wrote:As the invitation can go only once, hence this is a permutation without repetetion.

My answer is: 6X5X4=120.

I am no expert, but this is just my answer!

Letter,Letter,Letter,Letter,Letter, Servant

Is different from

Servent,Letter,Letter,Letter,Letter,Letter

and each of the 6 slots can be filled by either 1 of the 3 options (phone, letter or servant)

so the total num of ways = 3*3*3*3*3*3
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