a) In a sales campaign, for every item bought, shoppers are given a card with a picture of a film star on it. there are 10 different pictures and any shopper who collects a complete set of all 10 pictures wins a gift. on any occasion, a card recieved is equally likely to carry any one of the 10 pictures in the set. i) Find the prob that the 1st 4 cards received result in a shopper having exactly 3 different pictures.
ii) At a certain stage, a shopper has collected 9 out of the 10 pictures. find the least value of n such that P(at most n more cards are needed to complete the set) > 0.99
b) Susie has forgotten her pin number that consists of 4 digits in order. (The digits range from 0 - 9). She tries to recall her pin. Given that P(1st digit is correct) = 08., P(2nd digit is correct)= 0.86 and P(1st 2 digits are correct)=0.72. Find P(1st digit is incorrect and 2nd digit is incorrect).
2006-12-17
04:22:39
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1 answers
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asked by
Mathlover
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in
Mathematics