How many ways are there to choose three donuts from 4 varieties if there must be an odd number of glazed donuts? the number of glazed must be 1 or 3?

Respuesta :

1 glazed and 2 others     or     3 glazed and 0 others

           1 x 3 x 3               +                 1 x 1 x 1

                9                     +                       1

                                       10

Answer: 10