Question

A box contains 5 different red and 6 different white balls. In how many ways 6 balls be selected so that there are atleast two balls of each colour?

Answer 1

for selecting 6 balls so that atleast two balls of each colours = 5c2*6c4 + 5c3*6c3 + 5c4*6c2
          = 10*15 + 10*20 + 5*15 
          =150 + 200 + 75
            = 425              

Answer 2

for selecting 6 balls so that atleast two balls of each colours = 5c2*6c4 + 5c3*6c3 + 5c4*6c2
          = 10*15 + 10*20 + 5*15 
          =150 + 200 + 75
            = 425