Question

A lab technician took a fecal sample and did the following dilution.1. Transferred 0.1 ml from fecal sample to 9.9 ml saline in A2. Transferred 1 ml from A to 9 ml saline in B3. Transferred 0.01 ml from B to 9.99 ml saline in C.4. Transferred 0.1ml from C to an agar plate5. Counted 65 colonies on plate C What is the total dilution at C?

Answer 1

Step 1. 1:100

Step 2. 1:1000

Step 3. 1:100,000

Step-by-step explanation:

At first step, 0.1 ml is diluted in 9.9 ml of saline. Multiple both with 10 you will get 1 ml in 99 ml suggesting total dilution at first step as 1:100.

At second step, 1 ml of 100x dilution will be taken and further dissolved in the 9 ml of B3. Here, the dilution factor is further 10 times therefore the total dilution would be 1:1000.

At third step, 0.01 ml would be taken from 1000x dilution and further diluted in 9.99 ml. Therefore, the dilution factor here is 100 times. Hence the final dilution at this stage would be 1:100,000.

This is the simplest explanation I can give.

Hope it helps.