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Factorial Notation
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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

Unacademy user
Sir it would be 10 and 06
sir, I am not visualizing the formula of ncr and npr. how to prove it..
Doubt- in the lift question, we can consider 2 point of views... firstly, the 5 people can exit at 1st floor, 4 at 2nd floor and so on....and the other as u 1person can go to 7 probable which one is correct???and why
Why does a pair of stations is written?
okay bhaiya where you have written (n-1)! there should be (n+2)! then only 3(n+2)(n+1) will come it confused me a lot.
Rahul Chaudhary
9 months ago
because n will be canceled out with 2n and left 2
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