# 1. You spread 0.1 mL volume of a 10^(-5) dilution onto a nutrient agar plate. After 24 hours of incubation at 37°C, there were 223 colonies of bacteria on the plate.A.) What is the original concentration (OCD) of bacteria in the stock sample this dilution came from? B.) Using the OCD value from part A, determine the number of colonies that would be expected to grow on a plate that is inoculated with 0.1 mL volume of 10^(-7) dilution from this same stock of bacteria.

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1. You spread 0.1 mL volume of a 10^(-5) dilution onto a nutrient agar plate. After 24 hours of incubation at 37°C, there were 223 colonies of bacteria on the plate.

A.) What is the original concentration (OCD) of bacteria in the stock sample this dilution came from?
B.) Using the OCD value from part A, determine the number of colonies that would be expected to grow on a plate that is inoculated with 0.1 mL volume of 10^(-7) dilution from this same stock of bacteria.

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Step 1

In the given question

Volume of plate = 0.1 mL

Dilution = 10-5

Number of colonies formed = 223

• Original concentration (OCD) = number of colonies/ (dilution factor X volume plated)

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