SHOW YUUR WORK and include proper units in order to receive full credit. Be sure to note the volume that you are being asked about for determining a concentration (ie. 1mL v 100mL ). 1. What is the final volume when 0.2mL is added to 3.8mL diluent? 2. What is the dilution factor when 0.2mL is added to 3.8mL diluent? 3. You are examining Lake Lanier's E. cafi levels. Because you know the lake is really contaminated, you have collected 100mL of water and want to serially dilute the water 4 times, by adding 1mL of the sample to 9mL deionized water in the first dilution, and then three successive 1/10 dilutions. The last (fourth) dilution is plated, i.e. 1mL is plated on MI agar. After incubating the plate, 40 colonies are counted. How many colony-forming units (CFU) of E. colf were present per ml of original water? 4. A sample was diluted by placing a 0.1mL aliquot into 0.9mL of diluent, and 1mL of this dilution was plated. After incubation, 217 colonies appeared. What is the CFU/mL in the original specimen? 5. 250mL of drinking water was passed through a Millipore fitter, which was then plated on selective media for E. coll. 21 colonies matching the morphology for E. colf formed. What was the concentration of E. cofl in the sample in terms of CFU/100mL