There are 5 books on Mathematics and 6 books on Physics in a book shop. In how many ways can a student buy:
(i) a Mathematics book and a Physics book
(ii) either a Mathematics book or a Physics book?
(i) Given there are 5 books of mathematics and 6 books of physics. In order to buy one mathematics book number of ways are 5C1 similarly to buy one physics book number of ways are 6C1
Hence, the number of ways a student buy a Mathematics book and a Physics book is 5C1 × 6C1 = 5 × 6 = 30
(ii) Given there is a total of 11 books, so in order to buy either a Mathematics book or a Physics book it means that only one book out of eleven is bought.
Hence, the number of ways in which a student can either buy either a Mathematics book or a Physics book is 11C1 = 11
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