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Question
A student finds 7 books of his interest, but can borrow only three books. He wants to borrow Chemistry part II book only if Chemistry Part I can also be borrowed. Find the number of ways he can choose three books that he wants to borrow.
Solution
| Chemistry Part I borrowed |
Chemistry Part I not borrowed |
| Only one book from remaining 5 books borrowed | All three books borrowed from remaining 5 books |
|
Number of selections = 5C1 = 5 |
Number of selections = 5C3 = 10 |
Required Number = 5 + 10 = 15
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