Please help-Serial Dilutions

[viviruth]

Hello,

I have been assigned this problem to solve and I am not quite sure how to go about doing it.

You have a sample that has 7.0 x 10^9 cfu/ml of some organism. You are supposed to plate 0.1 ml to a petri dish to count 70 colonies. Draw the dilution series you would prepare, write the amounts of saline in the tubes, the amount you transfer in each step, and dilution factors of each tube you prepared. Circle the dilution you will plate 0.1 ml from to obtain 70 colonies after incubation.

I know that I have to take from the original sample and place it into other tubes to "dilute it," I am not certain about how to make it so I have 70 colonies.

Help would be greatly appreciated!

viv

[canalon]

Explained better than I would:
http://www.accessexcellence.org/AE/AEPC ... serial.php