Apurple flower with an unknown genotype is crossed with a white flower .determine the genotype of the purple if purple (p) is dominant and white (p) is recessive

   (Pp is the purple flower with the unknown genotype, pp is the white flower)

First scenario:
                                               Pp x pp 
       first generation:         Pp   Pp  pp  pp   (two purple, two white flowers)

Second scenario:              
                                               PP x pp
    second generation :     Pp  Pp  Pp  Pp  (four purple flowers)