Rooms for Guests ;)

A Gentleman has 6 spare rooms for guests. In how many ways can he accommodate 3 guests, each in a separate room?


The answer is 120.

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12 solutions

Hafsa Murtaza
Apr 21, 2014

there are 3 guests ,, each guest should have a separate room .. for this first guest has 6 choices of selecting his room.. he selects one room for him then second guest has 5 choices and he selects one room .. third guest has 4 choices... therefore 6 * 5 * 4=120 hence solved.. 120 is the ans.. :)

There are 6 rooms and only 3 have to be selected. The order of the room matters so we have to use permutation. 6P3=120

Abdur Rehman Ali - 7 years, 1 month ago

oopps it was a tricky one

Rahul Sharma - 7 years, 1 month ago
Abc Def
Apr 25, 2014

There are 6 spare rooms. 3 rooms can be selected of the 6 by 6C3=20.

The 3 guests can be arranged in 3 rooms by 3! ways=6

Total number of ways= 20x6= 120.

By using permutation we can solve.. That means the guest can be arranged in 6p3 ways

Kasani Suman - 7 years, 1 month ago

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Yeah, you're right. 6C3x3! Is the same as 6P3

Abc Def - 7 years, 1 month ago

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For combinations you would have to divide 120 for 3!(3x2x1), right? So you can only solve this problem through permutation.

Pedro Serzedelo - 7 years, 1 month ago

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@Pedro Serzedelo 6C3 [ (6!)/(3!3!) ]refers to selection of 3 objects(here rooms) out of 6. And then we multiply 3! to assure all possible arrangements of these objects (people in the 3 rooms). So we get 6C3x3!.

Where as 6P3 [ 6!/3! ] takes care of both selection and arrangement. This is why they are the same.

Abc Def - 7 years, 1 month ago

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@Abc Def Thank you :)

Pedro Serzedelo - 7 years, 1 month ago

Thanks for giving such nice solution

Adarsh Mahor - 5 years, 3 months ago

The first guest can be accommodated in any of the 6 different rooms. The second guest can be accommodated in any of the 5 remaining rooms. The third guest can be accommodated in any of the 4 remaining rooms. Therefore, total number of ways in which the guests can be accommodated= 6x5x4 = 120 :D :D

6!/(6-3)!=120

(6!)/(3!)?

Aareyan Manzoor
Oct 7, 2014

6!/3! . you get this how. there are 6 choice. so 6! but 3 geusts so6!/3!

Ashwani Singh
Oct 4, 2014

6 options...3 choices => \frac { 6! }{ 3! }

Lu Chee Ket
Aug 26, 2014

3! x 6 C 3 or 6 P 3 = 6 X 5 X 4 = 120

First: 6 ways;

Second: 5 ways;

Third: 4 ways;

Consecutive events: AND multiplication.

Vivek Prasan
Jun 19, 2014

Using permutation, 6P3 = 120.

Phuong Nguyen
May 11, 2014

it's like a simple problem: how many do you have to write a 3-number number from 6 numbers. and the answer will be: 6x5x4 = 120

Amit Patel
Apr 27, 2014

C 1 6 C 1 5 C 1 4 C^{6}_{1} * C^{5}_{1} * C^{4}_{1}

Aliki Patsalidou
Apr 27, 2014

is permutations of 6 over 3. 6 factorial over (6-3) factorial equals to120

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