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Grade Upto college levelAlgebra

A conference attended by 200 delegates is held in a hall. The hall has 7 doors,marked A,B,......,G. At each door,an entry book is kept and the delegates entering through that door sign in it in the order in which they enter . If each delegate is free to enter any time and through any door he likes, how many different sets of seven lista would arise in all ? (Assume that every person signs only at his first entry)

i) 206C6 ii) 199P5 iii) 199C5 iv) 206P6

plzzz xplain !!!!!!!!

Profile image of saurabh koshti
15 Years agoGrade Upto college level
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2 Answers

Profile image of SAGAR SINGH - IIT DELHI
15 Years ago

Dear student,

(200+7-1)C(7-1) = 206C6 (by n+r-1Cr-1)

Profile image of saurabh koshti
15 Years ago

ya i was getting the same answer but its not !!!!!! answer to this question is given as 206P6 in book !!