Question

A jar contains nine black buttons and seven brown if nine button are picked at random what is the probability that exactly five of them are black is it perm or comb

Answer 1

Explanation:

P=(9C5×7C4)/16C9

`9C5 * 7C4=(9*8*7*6*5)/(5*4*3*2*1) * (7*6*5*4)/(4*3*2*1)\\=9*7*2 *(7*5)\\=90*49\\\\=4410\\16C9=16C(16-9)=16C7\\=(16*15*14*13*12*11*10)/(7*6*5*4*3*2*1)\\=16*5*13*11\\=11440`

P=4410/11440=441/1144