Q.1 Out of 1000 families having 3 children each, how many would you expect to have (i) 2 boys and 1 girl, (ii) 2 girls and 1 boy?

Q.2 On an average 3 out of 10 students fail in examination. If 1000 samples each of 10 students are taken, in how many would you expect that (i) none has failed, (ii) all have failed?

Q.3 Assume that on an average one telephone number out of 15 called between 2 pm and 3 pm on weekdays is busy. What is the probability that if 6 randomly selected numbers are called (i) not more than 3, (ii) at least 3 will be busy?

Q.4 In a certain factory producing certain articles the probability that an article is defective is 1/500. The articles are supplied in packets of 10. Find approximately the number of packets containing (i) no defective, (ii) one defective, (iii) two defectives in a consignment of 20,000 packets?

Q.5 A manufacturer of pins knows that on an average 5% of his product are defective. He
sells pins in boxes of 100 and guarantees that no more than 4 pins will be defective. In
how many boxes out of 1000, he will meet the guaranteed quality?

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