Scenario #1

Dr. Furlong collected some pond water from Swan Lake.  She set up a dilution scheme and a plate count so she could determine the number of cells/ml in the lake water.  

Here is the dilution scheme:

bulletShe transferred 0.01ml of pond water to tube A, which contained 9.99ml of media.  
bulletNext she mixed up tube A and transferred 0.1ml of solution from tube A to tube B, which contained 99.9 ml of media.
bulletFinally, she transferred 0.1 ml of fluid from tube B to a plate and spread the culture across the plate.

She let the plate incubate for 24 hours and counted the number of colonies that appeared on the plate.  She counted 267 colonies.  

  1. What was the serial dilution at tube A?
  2. What was the serial dilution at tube B?
  3. What was the total dilution at Tube A?
  4. What was the total dilution at tube B?
  5. What was the number of cells per milliliter in the pond water?
  6. What was the number of cells per milliliter in tube B?

Scenario #2

Dr. Furlong collected urine from a patient.  She set up a dilution scheme and a plate count so she could determine the number of cells/ml in the urine.  

Here is the dilution scheme:

bulletShe transferred 1ml of urine to tube A, which contained 4 ml of media.  
bulletNext she mixed up tube A and transferred 0.1 ml of solution from tube A to tube B, which contained 4.9 ml of media.
bulletFinally, she transferred 1 ml of fluid from tube B to a plate and spread the culture across the plate.

She let the plate incubate for 24 hours and counted the number of colonies that appeared on the plate.  She counted 50 colonies.  

  1. What was the serial dilution at tube A?
  2. What was the serial dilution at tube B?
  3. What was the total dilution at Tube A?
  4. What was the total dilution at tube B?
  5. What was the number of cells per milliliter in the urine?
  6. What was the number of cells per milliliter in tube B?

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