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# Dilution Factors & Serial Dilution

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Seven test ubes each containing 4.5 ml of water are lined up.

0.5 ml of yeast culture is pipetted in to test tube #1. Then 0.5 ml of the solution form test tube #1 is pipetted into test tube #2. Then 0.5 ml of the solution for test tube #2 is pipetted into test tube # 3 and so on until 0.5 ml of the solution from test tube #6 is pipetted into test tube #7.

Question #1 Calculate the dilution factor for all 7 test test tubes. Show all work/calculations.

0.1 ml of the solution from the serial dilution 10^-4, 10^-5 and 10^-6 was pipetted onto three separate agar plates.

For the 10^-4 dilution because 0.1 ml is 1/10 (10^-1) of a milliliter the dilution represented on the plate is a 10^-5 dilution, not a 10^-4 dilution, the same goes for the 10^-5 and 10^-6 dilution.

The plates were left to incubate for a week. On the plate with the 10^-4 dilution sixty-eight colonies formed. On the plate with the 10^-5 dilution eighteen colonies formed. one the plate with the 10^-6 dilution one colony formed.

Question # 2 Based on the numbers of colonies formed calculate the cells per ml in serial dilution 10^-4, 10^-5 and 10^-6,. Show all work/calculations.