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Principle of Inclusion and Exclusion
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## Sachin Rana is teaching live on Unacademy Plus

Sachin Rana
IVth Year UG, IIT Bombay | YouTuber (143k subs) | Mentored 3 under 100 ranks in JEE Advanced | No. 1 educator for Organic Chemistry

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(19)
U
Unacademy user
thanks sir for the lessons
can any one explain me the ques of hw in last video which is explained in this video
For those who are confused how in the second question A intersection B is 96... here's how... see make a block of Britishers and Americans .. treat them both as 1 and 1 .. now total number of people would be 5 including the 2 from the blocks ... now number of ways would be { cause it is a circular permutation (n-1)! } (5-1)! × 2! × 2! that turns out to be 96 .. :)
Rohit Yadav
7 months ago
for those who are still confused.. first two factorial is for Americans as a whole and British as sa whole arranging and the second one is for their interrnal arranggement
A intersection B = 4! x 2! x 2! = 96..REASON ---- this is the case when 2 American and 2 British take as 1 Now we have 5 people they sit on round table we take (5-1)! , 2! for arranging 2 Americans similarly for Britishers
5026 HW answer
how did you get a intersection b in the nationality question if possible tell me my mistake too we can consider the group of Dutch and britishers to sit together that we consider them to be a single quantity and number of ways to arrange them with the others is 2! and now the people inside of this quantity can be arranged in 2! number of ways hence 4
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