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प्रश्न
How many different selections of 5 books can be made from 12 different books if, Two particular books are never selected?
उत्तर
Two particular books are never selected.
Since two books are never selected.
The total number of books is 10.
∴ The number of ways of selecting 5 books from 10 books
= 10C5
= `(10!)/(5! xx (10 - 5)!)`
= `(10!)/(5! xx 5!)`
= `(10 xx 9 xx 8 xx 7 xx 6 xx 5!)/(5! xx 5!)`
= `(10 xx 9 xx 8 xx 7 xx 6)/(5!)`
= `(10 xx 9 xx 8 xx 7 xx 6)/(5 xx 4 xx 3 xx 2 xx 1)`
= 2 × 9 × 2 × 7
= 252 ways
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