An industrial microbiologist wants to estimate the total population of a yeast culture in a 450 cm³ fermentation vessel.

The microbiologist uses the following method:

• Extract a 5 cm³ sample of the yeast culture from the vessel.
• Perform a serial dilution series consisting of four 5-fold dilutions. Each step is carried out by transferring 2 cm³ of the suspension into a tube containing 8 cm³ of sterile nutrient broth.
• Pipette 0.2 cm³ of the final diluted mixture onto an agar plate and spread it.
• Incubate the plate for 24 hours and count the resulting colonies.

A total of 48 colonies are counted on the plate.