Estimate the final fold dilution for the diluted solution

Assume you were given fifty ml of sewage and asked to determine the number of bacteria in the sample. You began by taking 5 ml and putting it into 45 ml of sterile water. From this mixture, you took 1 ml and put it into 99 ml of sterile water. From the previous mixture, you took 10 ml and put it into 10 ml of sterile water. From the previous mixture, you took 1 ml and put it into 9 ml of sterile water. From the previous mixture, you took 5 ml and put it into 45 ml of sterile water. Then, you plated 0.2 ml of the final solution, 0.1 ml and 0.01 ml, all in triplicate. The plates inoculated with 0.2 ml and 0.1 ml of the solution had TNTC (too numerous to count) and the 0.01 ml plating generated 51, 49 and 32 colonies.

a. What is the final fold-dilution for the diluted solution used for plating?

b. What are the bacterial counts per ml of original sample?

c. What are the total bacteria counts in the original sample?

 

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