Sagot :
If the bag contains 7 white balls and 5 black balls,
C(n,r) = C(12,5)
= 12!(5!(12−5)!)
= 12!/(5!×7!)
= 792 ways
If the bag contains 3 white balls and 2 black balls,
C(n,r) = C(5,5)
= 5!(5!(5−5)!)
= 5!(5!×0!)
= 1 way
If the bag contains 7 white balls and 5 black balls,
C(n,r) = C(12,5)
= 12!(5!(12−5)!)
= 12!/(5!×7!)
= 792 ways
If the bag contains 3 white balls and 2 black balls,
C(n,r) = C(5,5)
= 5!(5!(5−5)!)
= 5!(5!×0!)
= 1 way