oo Ooredoo 4G 12:10 PM mybb.qu.edu.qa Problem#1 In your classroom there are 40 s
ID: 2926270 • Letter: O
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oo Ooredoo 4G 12:10 PM mybb.qu.edu.qa Problem#1 In your classroom there are 40 students, assume that none of them is born on February 29, and hence consider only common years (365 days) [do not consider leap years]. 1- Take a student randomly from the class, what is the probability that he have the same birthday as yours? Write your answer here (do that for all questions) 2- What is the probability that there is at least one student in the class having the same birthday as yours? 3-What is the probability that there is no repeated birthday date in the class (all the 40 birthdays being different)? Comment on the value you found 4- The instructor decides to nominate 5 students randomly to deliver a presentation next class, How many groups (of five students) are possible? What is the probability that you are among the selected students? Problem#2 A firm has ordered a batch of identical electronic deviceExplanation / Answer
1.probability that she have the same birthday as yours =1/365
2) probability that there is at least one student in the class having the same birthday as yours= 1- probability that none of them share birthday with you
=1-(364/365)39
3)for no repeated birthday 1st person can have birthday on any date, second on remaining 364 days , 3rd on remaining 363 days and so on
hence probability =365*364*363*...........*321/(365)40=0.0340
probabilty of that happening is not very rare it is 3.4%
4)number of ways to take 5 out of 40 =40!/(5!*35!) =658008
as i have to be among the 5 , number of ways rest 4 can be chosen out of 39 =(39!/4!35!) =82251
hence probability that you are among the selected students =82251/658008=0.125
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