Number of ways 4 couples sit in a row with couples together IIT JEE

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Organized Counting
Fundamentals of Counting Principles
Permutations and Factorials
Principle of Inclusion and Exclusion

[arinzeanthony]

I agree with everything you did except for part C.
The 4 men can be further arranged in 4! Ways.
Making it 120×4! = 2880.
I think that should be the answer.

[cherrypinati]

Sir in part c
U didn't arrange the 4 men
U did only select them
There 120 should be multiplied by 4! and final answer becomes 2880.

[saroja]

Sir I one of the question for boys and girls arrangements ....for no two boys sit together u taken 5p4 now why u taken 5c4 for no men sit together

[NantambiHellen-fdzw]

thanks for your knowledge but I think after getting the answer in b we multiply it by 2 factorial coz the ladies can change position with the men. they can either sit at the extreme end then men in the beginning

[henrysungula]

The answer for part c is incomplete. Of course there are five combination 4 ways of positioning, but you did not take into account the number of arrangements for the 4 men

[musabr.]

Part c is incorrect - It should be 4! 4! 2.
_ m _ m _ m _ m so 4! for men and 4! for women. now men can also be in the first place so multiplied by 2.

[bharatijoshi]

Sir for part c I think the answer should be this way
Total arrangements - ways in which all men sitting together
That is 8p8 - 5p5×4or
Where p denotes permutation
Sir let me know if this is wrong

[rahulchoudharybhardwaj]

The answer to last part, according to your method, would be 8×6×5×4×3×2×1×1 (I guess).
Please do let me know if I'm wrong

[mathwiztube]

AA .I am gul Hassan from Pakistan.I cannot explain my feelings to listen your lectures.Please recommend me an easy book regarding number forming.Also I have a question,
"How many four-digit numbers formed of only odd digits are divisible by five ?".
I hope you will guide me.

[mohitarora]

may be your answer to he 3rd part is incorrect. it should be 4! * (5c4) *4!

[milliekatwere]

(No couples sitting together) is the same as (each couple sitting together)

[JosephAPS]

Hi - Can you post the answer to part e ?

[patrickeklu]

thanks.please can you help me come out with this two questions.


question1:In how many numbers of two different digits can be formed by using the digits 1, 2, 3, 4 if repetition of digits is not allowed?
Question2: a bag contains 4 red balls and n number of blue balls. All the balls are the same except for colour.
Two balls are selected at random from the bag one after the other without replacement.If the probability of selecting a red ball and a blue ball is=5/9, find the number of blue balls in the bag.
Thank you Sir

[freedommulovhedzi]

Very nice! Can you please help me with this one: How many 3 digits numbers that are multiples of 4 can be formed from the six digit 2, 4, 5, 7, 8, 9?

[tanishkkumar]

from 7 married couples by how many ways 4 persons can we selected so that no husband and wife in selection?

[mukeshrani]

Why didn't you permutate all men in (c) part, pl tell.

[remilekungiwa]

in how many ways can the letter of the word ELEVEN be arranged such that vowels occupy alternate positions

[ayanaxhye]

Hey why is 4:47 5C4 and not 5P4? Please let me know

[noraiseni]

what if the couples cant sit next to each other ?

[abaegbuemmanuel]

Sir please when you group all the ssss together in Mississippi you didn't did not write the ssss as 4factoria like you did in the one for the ladies please sir explain