A bag contains 7 white balls and 5 black balls. 5 balls are drawn at random. In how many ways can the 5 balls be drawn from 12 balls? If 3 balls are white and 2 balls are black? SHOW YOUR SOLUTION

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