Question

2 ml of stock antibiotic (64 mg/ml) was diluted into a test tube containing 2 ml of broth (final volume is 4). A series of 2-fold SERIAL DILUTIONS were performed by transferring 2 ml to three other tubes, consecutively (final volumes now 2 ml in each tube). The final concentrations of antibiotic in the four tubes are: 32, 16, 8, and 4.

Next, 2 ml of water were added to each each tube individually (not a serial dilution). What is the final concentration of antibiotics in the tubes?

Answer 1

I think this is another 2-fold dilution where the answers are 16, 8, 4, and 2, but I'm not sure.