Your starting culture already had a dilution of 10^-3.
Three serial dilutions of 1/10 were made from that dilution. A
volume of 0.1ml was plated from each dilution. After incubation, the
colony counts were 589, 146, and 9 respectively, for the 3 dilutions
plated.
What is the dilution factor of the countable plate? Use starting
culture x dilution(s) necessary to get to the countable plate x plating
dilution.
10^-3
10^-4
10^-5
10^-6
10^-7
10^-8
10^-9
10^-10