e E. viable count QUESTION 9 Imagine that you have done a membrane fitration cou
ID: 252564 • Letter: E
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e E. viable count QUESTION 9 Imagine that you have done a membrane fitration count for Escherichia coli on E col agar using 250 ml of ell water. The count reveals an average of 54 colonies on the plates. Which of the following best reflects the number of E col in the well sample? e A 108/100 mL B. 54/100 ml. O C.54/1000 mL D. 21.6/100 mL E 10.8/100 ml QUESTION 10 In a dilution scheme. 1 mL of the original sample has been added to 99 ml of diluent Which of the following would be the next dilution operation if you wanted to obtain a total dilution of 1/10 000 of the original sample? A. 1 ml to a 9-ml dilution blank B 0.1 ml to a 9-ml dilution blank C 1 mL to a 999-ml dilution blank D 0.1 ml to a 99-mL dilution blank E 0.1 mL to a 9.9-mL dilution blank Chick Save and Submit roave and mbinih ic SadaExplanation / Answer
9. 54 colonies per 250 ml can be reduced to 21.6 colonies per 100 ml. both are same. (54/2.5 = 21.6). Option D.
10. 1 ml added to 99 ml gives 1/100 (or 10-2) dilution. we need a final dilution of 1/10000 (or 10-4). therefore, we can again add 1 ml of the first dilution to 99 ml. however, this is not given in the options. divide both by 10, which gives 0.1 ml to be added to 9.9 ml. (option E)
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