If you count 60 colonies after generating a dilution factor of 10^-8 and plating 100 microliters, what is the starting concentration?

CFU / ml = 600 x 10⁻⁸

Explanation:

Given:

Number of colonies = 60

Dilution factor = 10⁻⁸

Volume plated = 100 micro-liters = 0/1 ml

Find:

Starting concentration

Computation:

CFU / ml = [Number of colonies x Dilution factor] / Volume plated

CFU / ml = [60 x 10⁻⁸] / 0.1

CFU / ml = 600 x 10⁻⁸

the correct option is option a

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